F( ..-bruir/1977 45p - americanradiohistory.com...*Care is a system of digital data storage which...

F(_..-bruir/1977 45p

Announ.--- r- --"N

I I r r

00 *

Cadac Automated Recording/Remix Equipment

*Care is a system of digital data storage whichcan store, retrieve and update the settings of ananalogue and switching functions of a mixing

console.

Pye Records chose a Cadac Carec'equippedconsole for their new London studios.

c dlr.1

Cadac, first in European audio technology.

Cadac (London) Ltd.141, Lower Luton Road, Harpenden, Herts AL51:Harpenden (STD 05827) 64351 Telex 8263

Cadac (Holland) B.V.G.V. Amstelstraat 97, Hilversum, Holland'Z:0215017722 Telex 43834

EDITOR RAY CARTERTECHNICAL EDITOR FRANK OGDENEDITORIAL PRODUCTION

DRUSILLA DALRYMPLECONSULTANT HUGH FORDSECRETARY WENDY SMEETHEXECUTIVE ADVERTISEMENTMANAGER

DOUGLAS G. SHUARDADVERTISEMENT MANAGER

TONY NEWMAN

PTHE LINK HOUSE GROUP

Editorial and Advertising Offices:LINK HOUSE, DINGWALL AVENUE,CROYDON CR9 2TA, ENGLANDTelephone: 01-686 2599Telex : 947709Telegrams: Aviculture Croydonc) Link House Holdings Ltd 1976All rights reserved.

TUDIO SOUND is published on the 14th of theveceding month unless that date falls on a Sundaywhen it appears on the Saturday.

SUBSCRIPTIONS4/I enquiries to: Subscription Dept, Link House, 25Vest Street, Poole, Dorset BH15 ILL. Poole (02013)'1171.

)ISTRIBUTION;TUDIO SOUND, published monthly, enables engin-ers and studio management to keep abreast of newechnical and commercial developments in electronicommunication. It is available without charge toualified readers; these are directors managers,xecutives and key personnel actively engaged in theound recording, broadcasting and cinematographsdustries in any part of the world. Non -qualifyingeaders can buy STUDIO SOUND at an annualubscription of £7.60(UK) or £7.20 (Overseas). Expressair mail) as follows (extra charge over paid or freeubscription): Argentina (B), Angola (B), AustraliaC), Austria (X), Barbados (B), Belgium (X), BermudaB), Botswana (B), Brazil (B), Bulgaria (X), CanadaB), Chile (B), Colombia (B), Cyprus (X), DenmarkX), Finland (X), France (X), Ghana (B), Greece (X),lolland (X), Hong Kong (B), Hungary (X), IcelandX), India (B), Indonesia (B), Iran (A), Israel (A),taly (X), Jamaica (B), Japan (C), Kenya (B), LebanonA), Malawi (B), Malaysia (B), Mexico (B), MonacoX), New Zealand (C), Nigeria (B), Norway (X), PeruB), Philippines (C), Poland (X), Portugal (X),thodesia (B), Rumania (X), Singapore (B), SouthAfrica (B), Spain (X), Sri Lanka (B), Sweden (X),;witzerland (X), Tanzania (B), Thailand (B), TrinidadB), USA (B), Virgin Islands (B), West Germany (X),'ugoslavia (X), Zambia (B).

ConesK Europe goes air mail regardless 2nd class air maile1 £18.78 (12 issues)3 £18.84 (12 issues)

£22.56 (12 issues)

3INDER Soose-leaf binders for annual volumes of STUDIO;OUND are available from Modern Bookbinders,:hadwick Street, Blackburn, Lancashire. Price is2.00 (UK and overseas) Please quote the volumeumber or date when ordering.

ABCMEMOIR OP 1MI AUDIT1111...41 0/ ONVIATICKS

'otal average net circulation of 8899 per issue during975. UK: 5689 overseas: 3210. rota/ average netirculation of 10 030 for January 1976. UK: 6003,verseas: 4027

studio soundAND BROADCAST ENGINEERING

Every studio manager has a short list of the most desirable qualities for any given control room;usually his own will possess more of them than the studio across the street/town/world. A con-sensus of opinion would most probably indicate that 'good acoustics' head that list.

However, further investigation of that particular quality would be a relatively useless exercise;the revelation that control rooms should provide a 'nice tight bass sound with lots of crisp top'isn't exactly earth shattering. In spite of such easy conclusions, one fact, albeit negative, willemerge. There are few studio people who will attempt to describe acoustics, whether talking abouttheir own studio or generalising, in terms of Hz and dB. If they do, they are more likely to bespecnologists than recording engineers. Actually, this is very surprising considering the quantityof blurb surrounding other bits which make up a control room.

On the desk, nearly every function is dutifully inscribed in dB or Hz (pan is about the only onethat isn't). On compressor limiters, equalisers and monitoring circuits, dB and Hz abound inpro and con fusion. Loudspeaker manufacturers nearly always quote millions of dB's to add tolistening pleasure. So how strange it is that real live, two eared people talk about 'tight bass andtinkly treble' rather than -4 dB at 63 Hz (ISO centre 1 -octave pink noise) and +6 dB at 12.5 kHz,etc. One can only suppose that God provided almost everybody except the spec writers with apair of ear drums instead of B & K spectrum analysers, but such are the imperfections of Creation.

Lesser individuals such as recording engineers have to use their ears to monitor the effects ofsubtle changes in eq; in time, a certain adjustment to the number of dB and Hz as shown on thedesk will become associated with a particular audible change but the process is never the otherway round. From this, the function of desk calibrations may be understood. But what of thelearned gentlemen who make their living by quantifying the acoustics of other peoples' studios-the consultants?

In this issue, George Augspurger, a much respected US acoustician tells of his approach inrelating objective acoustic measurement to subjective effect. He also describes what can and can'tbe achieved with monitor equalisation. He would never suggest that his instruments can predictconditions for the perfect acoustic balance-that changes every time a new face sits in front ofthe mixing console-but they can isolate areas where problems may be expected, if not alreadypresent.

More often than not, Mr Augspurger's instruments provide the starting point for subjectivediscussion.

contentsFEATURESMONITOR EQUALISATIONGeorge Augspurger 26

SURVEY: TEST GEAR 30

TAPE MACHINE MAINTENANCEDave Dearden 36

SURVEY: TEST DISCS AND TEST TAPES 40

COLUMNSNEWS 20

LETTERS 38

WORK 42

REVIEWSRADFORD LOW DISTORTION OSCILLATC RHugh Ford

RADFORD DISTORTION MEASURING SETHugh Ford

50

54

AMBER 4400 MULTIPURPOSE AUDIO TEST SETHugh Ford 58

BRUEL & KJAER PSOPHOMETFRHugh Ford 64

FEBRUARY 1977 VOLUME 19 NUMBER 2

It's the Compex Limiter F760X-RS.Over 800 studios around the

world use it, and are delighted with it.Because it has so many

advantages.It saves money.

One instrument, with one set ofline amps, instead of three.It's handy to use.

All the functions are controlledon one front panel.It's electronically excellent.

With only one set of line ampsyou get less noise and less signaldegradation.

It's totally reliable.Versions have been in use for

over 5 years without a singlebreakdown.

The technical specifications aresuperb. Send for full data; in themeantime, here are a few pointers.

Compressor. 5 compressionratios, 3 attack times, 8 release times,and a special automatic network togive a very fast release over tran-sients of 6dB or more, on a longplatform.

Expander. A 0-20dB range with a2:1 slope, an optional gate position

giving a 20:1 slope, and a releasetime continuously variable between25ms and 5 seconds.

Peak Limiter. A fixed thresholdproviding exceptionally low noiseand distortion, with output attenuatorto vary the effective threshold from+14dBm downwards.audio & design recording ltdSt. Michaels, Shinfield Road,Reading, Berks, UK.Telephone: Reading (0734) 84487.Telex: 847605.

Manufacturing members APRS

It compresses,expands andlimits,all in one go.

We makesound

REPRESENTED IN: USA -CANADA -AUSTRALIA -NEW ZEALAND -JAPAN -SOUTH AFRICA -BRAZIL -EASTERN EUROPE -BELGIUM -DENMARK -FINLAND -FRANCE -WEST GERMANY -GREECE- HOLLAND -ITALY -NORWAY -SWEDEN- SWITZERLAND

TRAVELLING LIGHTWITH RUGGED, PORTABLE MIXERS FROM AUDIO DEVELOPMENTS

Our wide range of Portable Mixing Consolesare designed and built to the highest technical specification

and are in use world wideby the most discerning of professionals.

Because we realise that some of our clientsfind themselves working in strange out of the way places

but still requiring studio quality away from studio conditions,we've made our battery operated mixers

extra light and extra rugged to stand up to therigours of arduous travel and useage.

No matter what your mixing requirementsare we've got a unit to suit you - so contact us today

and we'll give you some sound advice.

AudioDEVELOPMENTS

HALL LANE, WALSALL WOOD, WALSALL,WEST MIDLANDS WS9 9AU.

Telephone: BROWNHILLS (STD Code 05433) 5351

International Agents:

M. R. Drott,Johannesgasse 18,A-1015 Wien,Austria

Phillips ElectronicIndustries Limited,200 Consumers Road,Suite 105,Willowdale, Ontario,Canada

Kinovox,lndustrivej 9,DK 3540, Lynge.Telephone: 03 18 76 17Denmark

Studio Centre,3 Rue Du Telegraphe,75020 Paris,France

Sound Techniques,Postbus 206,Al maar,Holland

Laboacustica,Via Muggia 33,00195 Roma,Tel: 3595506/386867Italy

Siv Ing Benum and Co.,Boks 2493,Solli, Oslo 2,Norway

Intelec (Pty) Limited,P.O. Box 25048,Ferreirastown,South Africa

Dr. W. A. Gunther,lngenieurburo SIA,8702 Zollikon, Zurich,Seestrasse 49-51Switzerland

Austerl itzElectronics GmbH,85 Nurnberg 1,Postfach 606West Germany

5

Stereo and 4 Track Mixing Consoles

4 -band equalisation

Low noise circuitry -125 dBm ref inent Low distortion -0.01% typically Line level and mic level inputs Line level outputs up to +22 dBm

Prefade listen and talkback optionallyavailable

Ideal for use with Teac, Revox,etc.Also available graphic and parametricequalisers, disc preamp units andcrossovers

Further detailscontact ELECTRONICS

Lampas House, Kneesworth St.,Royston, Herts. 0763 45214

REW are proud to present the Soundcraftsmen Graphic Equalizer-undoubtedlythe finest unit of its kind for both Hi-Fi and professional use. Each of the stereochannels is divided into 10 frequency bands, from 20 Hz to 20,480 Hz. Boostand cut of 12 dB is provided on each band and a gain control adjusts the outputto match any amplifier. The unit has a champagne gold anodised front panel,enclosed in an attractive wood -grained cabinet. The Soundcraftsmen can beused as a sophisticated tone control enabling you to highlight individual instru-ments. Alternatively it can be used to produce a near -perfect flat frequencyresponse in any domestic conditions by compensating for either poor roomacoustics or various deficiencies in Loudspeakers. Also perfect for equalizingtape recordings. Send for full literature.Full range of Equalizers by other leading manufacturers also in stock includingAltec, JVC, BSR, MXR, Technics.

Main West End Dealers:REW Centrepoint,20-21 St Giles High Street,London WC2. Tel: 01-240 3066/7. 230 Tottenham Court Road,London WI. Tel: 01-637 2624/5.I46 Charing Cross Road,London WC2. Tel: 01-240 3064/5.

TRADE ENQUIRIES: D.E.S. Technical Co, 10-12 High St,Colliers Wood, London SWI9. Tel: 01-540 8944.

A6 STUDIO SOUND, FEBRUARY 1977

RE

SHEFFIELD SOUND CENTRE

SPECIALISTS IN HI-FI

Main agents for Teac, Tascam, AR, Uher, DokorcRevox, Spendor, JBL, Dahlquist, Tannoy, Cerwin-VEFerrograph, Marantz, Bic Technics, Quad, ArmstrcSony, Nagra, IMF, Dbx, Otari, and many me

Competitive prices, terms, part exchange

101a and 107 ECCLESALL ROADTel : 0742 23365

STUDIO EQUIPMENT SERVICSupply UHER, TASCAM, TEAC, REVO)

We believe good back up services are essential.to delivery all machines are fully checked, modas required and biased to client's tape. After dellrapid repair and maintenance services.

I. DOWNS 01-200 1229

From now on, it's either theAmpex ATR-1 00 or somethingless!

This incredible recorder hasbeen developed to give you thesort of performance and re-liability that you have neverexperienced before.

Its transient response, head-room and better tape handling

AMPEX

system will enable you toachieve recording standardsthat you've never touched inthe past. Ampex ATR-1 00 -it's the only choice for the realprofessional.

Call Tony Shields at thenumber below - he's got somevery interesting literature thatyou should see.

Ampex Great Britain Limited,Acre Road, Reading, Berkshire.Tel: 85200. Telex: 848345

7

Alice STILL MAKING QUIET MIXERS

Call Ted Fletcher - he'll tell you more

NOISE PERFORMANCE ALICE 62/3BNoise measured at 70 dB gain (voltagereferenced).20Hz to 20KHz unweighted R.M.S. 128.5 dBbelow input across 200 ohm input load.Measurement according to I.B.A. Code ofPractice.Noise measured peak with precisionP.P.M. 70 dB gain referenced to 0 dBm output.Unweighted 20Hz to 20KHz -52 dBm (CodeLimit -48.5 dBm). Weighted CCIR Rec 468-46 dBm (Code Limit -40dBm).(The I.B.A. Code of Practice refers to completesignal paths but the test remains valid for asingle mixer because noise in a system orig-inates predominantly from the first micro-phone amplifier stage.)Frequency response of measured system +0.5 dB 40Hz to 20KHz at 0 dBm output and70 dB gain.Channel overload margin greater than 30 dB.

(Stancoil Ltd), Sales Office, Alexandra Road, Windsor, Berks.Phone Windsor 51056 Telex 849323 Aegis G

DOKORDER4 CHANNEL TAPE DECKSfor Mini Studio useDOKORDER 8140Ideal machine for minidomestic studio use. Allowspossibility for multi -trackingwith built-in sync facility.High specification at lowprice. Superb for makingdemo tapes.

DOKORDER 7140Basically similar to 8140 butslightly less luxurious version.

DOKORDER 1140Top quality high speedmulti -sync, 4 -channelrecorder.

DOKORDER 1120Two channel +-track deckoffering facilities andperformance normally foundin much higher priced decks.

DOKORDER 7100Budget priced stereo deck,ideal for the domestic user.Main West End Dealers:

RE 146 Charing Cross Road,London WC2.Tel:0I-240 3064/5 230 Tottenham Court Road,London WI. Tel: 01-637 2624/5

TRADE ENQUIRIES: D.E.S. Technical Co., 10-12 High St.,Colliers Wood, London SWI9. Tel: 01-540 8944.

8 STUDIO SOUND, FEBRUARY 1977

tAUDIO MODULES 'gBUILD YOUR OWN

eMixers , Consoles,or add on to old equipt.

easy to use

10 different MODELSmic (Low-Z,Hi-Z), Mag. Phono, NAB Tape,Active Equalizer, Line Amp, Power Amp .

From $16.50 to $43.50 Pro-NET(domestic)check your nearest distributor for local prices.

Send for NEW Catalog over 280 items for At

SESCOM foreign distributors:Australia: Klarion Enterprises Pty. Ltd., So. MelboureCanada: Chas. L. Thompson, Ltd., No. Vancouver BC

John R. Tilton Ltd., Scarbough Ont.England: Future Film Developments, LondonGreece: Laboacustica Hellas: AthensHolland: lemke Roots Import ,AmsterdamItaly: Laboacustia Srl, RomaNorway: Roger Arnhoff Studio a.s.,Oslo

SESCOM, INC.

"QUALITY ENGINEERED SOUND PROUDUCTS.P.O. Box 590,Gardena,CA 90247 USA(213) 770 3510 ,TWX 910 346 7023

Sweet sixteenThe Quad 405 is only the sixteenthproduct to carry the Quad name,each of which, has made asignificant contribution to thedevelopment of sound reproductionand acquired a following of loyaland satisfied customers

The Quad 405 current dumpingamplifier represents another stepforward in amplifier technology,executed with the attention toengineering and aesthetic detail,

and manufactured with the concernfor reliability which have beenthe hallmarks of Quad equipmentfor twenty-five years.For further details on currentdumping and other Quad productswrite to Dept. SSThe Acoustical Manufacturing Co.Ltd., HUNTINGDON, Cambs.,PE1 8 7DB Telephone (0480) 52561

QUAD Design CouncilAward 1976

for the closest approach to the original sound for twenty-five yearsQUAD is a Registered Trade Mark

Rogan Squint'sthe specialists in equipment for radio studi(PROFESSIONAL EQUIPMENT AT COMPETITIVE PRICES FOR BO'BROADCASTING STUDIOS -AND RADIO RECORDING STUDIO

ALL PRICES ARE NETT PROFESSIONAL

BROADCAST TURNTABLESCARTRIDGE MACHINES

r1IM :r.;-°

SQUIRE S3000 Mk. IIR/Playback compat. £175

TAPECASTER X700full range, from £470

RUSSCO from £202

INSTANTSTART

QRK I2CE £190(arm extra)

BRAND NEW ! PRODUCTIONMIXER FROM ALLEN & HEATH.

STEREO D.J. SELF -OP, 6CH,MANY FEATURES - £350

Allen and Heath MINIMIXERS6 into 2 - ONLY L148

Chilton MixersPRICES FROM £410

SID " SID04

I I 1

4

4 4 110 111'

1

0 0 $ ' Co

FEATURING

Remote startsVoice auto fadeFull studio spec.

Squire S4000 6ch M/S Mixer £251

ALLEN & HEPOP MIXER!

16/2 ...14/2 ...12/2 ...10/2 ...

Ex -demo Spotmaster Model 1000 cartridge machines at special prices. Alice STM 6 portable 6 channel stereo transmission mixer ... £465.1

Stanton 500 AL Cartridges £16.60 Budget -priced mic/gram mixers, from ... E65.1

AKG Studio Mics, from ... £58.00 Uher Interview Recorders ... £242.1Anglepoise Mic Stands ... E14.75 HH variable echo units ... £1341

ALSOUK CUSTOMERS VAT EXTRA

DELIVERY ANYWHERE IN UK PLUS EXPORT SERVICEMost items available ex -stock. Prices subject to change without notice.

Imported goods subject to changes in exchange rates.SHOWROOMS OPEN TUESDAY - SATURDAY. CLOSED MONDAYS

OPENING TIMES 10.00 a.m.-5.00 p.m. LATE NIGHT WEDNESDAYS UNTIL 8.00 p.m.

Talk to our Manager Tony Kingsley.He knows about Radio Studios.

SOME ITEMS ALSO AVAILABLE FROMOUR MANCHESTER BRANCH.10 STUDIO SOUND, FEBRUARY 1977

Rogan Squint'sSTUDIO EQUIPMENT DIVISION55 CHARLBERT STREET, LONDON NWETelephone 01-722 8111

GAUSS SLAVES NEVERSTOP WORKINGAll over the world they are to be found working away ... in the USA, Argentina,England, Scotland, Netherlands, Italy, Malasia, France, Australia, Canada, Sweden,Germany, Norway, Japan, Mexico, Greece, Switzerland, Spain, Portugal, Belgium,Hungary, Indonesia, South Africa, Egypt, Singapore, New Zealand ... in every majorduplicating company Gauss slave recorders keep up the world's highest productionrate, all the while raising the standard of quality tape duplication and retaining thatextraordinary sound that has kept Gauss the leaders in tape duplication - worldwide.

NOW

64 :1!The Series 1200 System comprises a Master Reproducer model 1210 (1",-f' and versions available) in conjunction with Gauss' exclusive horizontalpneumatically driven Loop Bin. Up to 20 slaves can be controlled, eachusing the Gauss unique Ferrite record head (10 MHz bias).

* With duplicating ratio of 32:1.* The ultimate in gentle handling of master tapes.* The World Standard in pre-recorded music duplication quality for

cassette and cartridge programmes.

CetecEUROPEAN OFFICE

SAPPHIRE HOUSE, 16 UXBRIDGE ROAD, EALING, LONDON W5 2BP. Telephone: 01-579 9145 Telex: 935847' MAIN OFFICECETEC AUDIO a Division of Cetec Corporation, 13035 SATICOY ST., P.O. BOX 3941, NORTH HOLLYWOOD, CALIFORNIA 91605, U.S.A. Tel: (213) 875-1900, T.W.X. (910) 499-2669.

complete thepicture...

...with their new NAGRA EA dilemma Nagra were suffering for some time, was how to produce a self-contained Professional Tape Recorder which incorporated all the qualities oftheir highly acclaimed Nagra 4.2, but could be marketed in the lower pricerange. Almost anyone can manufacture a cheaper version of a successfulproduct but Nagra were determined not to sacrifice standards for economy.Well, we are happy to announce they have achieved the perfect solution withthe new Nagra E.The astounding saving of around 50% has been principally achieved by thesimplification of the speed stabiliser-a single operating speed of 71/2 ips isprovided. The tape deck and transport mechanism are closely similar to that

TECHNICAL DATADimensions: 13.8 x 9.3 x 4in (351 x 336 x 104 mm)Weight: 12.6 lbs (5.75 kg) with tape and batteriesWow and flutter: ±. 0.1%

Reels: 7 in cover open, 5 in cover closed.

Loudspeaker:1.0W both switchable Tape/DirectHeadphones outputFrequency response recorded at -20 dB: 30-15.000 Hz 2 dBSIN ratio, ASA"A": better than 66dBTemperature range: 4°-158°F(-30 to + 70°C)


used on the Nagra 4 Series, which has become renowned worldwide for itsreliability and performance.Good news, for the operator in the field, is that the new model is slimmer andlighter than the 4.2 and comes complete with a measuring probe, circuit dia.gram and some essential spares. This means that bias adjustment resultingfrom tape type change can be easily carried out away from base. A singlemicrophone Input is provided which can be switched to accept dynamic orcondenser types.

MMMMMMMM MMMMMM INIII Ell NM MIPlease send me further details of the new NAGRA E and other modein the range.

Name

Address

HAYDENHAYDEN LABORATORIES LTDHayden House, Churchfield Road, Chalfont St. PeterBucks, SL9 SEW Tel: Gerrards Cross 88447

SS2

L Mill MMMMMMMMMMM w IIII

0 TAIndustrial TapeApplications

CHANGE OF ADDRESSITA's new showroom, service and distribution

centre is now located for easier access and parkingfacilities at:

1-7 Harewood Avenue,Marylebone Road, London NW1.

Tel: 01-485 6162/7833.Telex: 21879.

London's only supplier fully geared to the needsof the recording and industrial equipment user.On demonstration, equipment by REVOX, TEAC,

TASCAM, ITAM, OTARI, AKG, H & H, QUAD, ALLEN &HEATH, TRIDENT, 3M, AUDIO & DESIGN, KLARK-TEKNIK, AUCE, DBX, ORBAN PARASOUND, etc.

3000sq.ft. of showroom and service area.

FCCCr:JEZr-jr-,

tlfttliiits*ikik111....1,,,

*411Viks %S** i 6*tireo41.*******$ . I

b.* s * ge II:VINO

.... It

At ITA you can find London'sbiggest range of tape recorders,mixers and ancillary equipment.Backed by fully professionalservice by our own technicians.

TEACFour 4 -channel machines

from £405

TEAC TASCAMNew range of mixers

including the mini 6 -input Model2 and two 4 -output mixers,Models 3 and 5

ITAM4 and 8 output mixers

£690-D260ALICE

AD62 well establishedstereo mixer £249

OTARIWide range of

professional equipmentincluding stereo, 4 -channel and8 -channel recorders. And theworld's finest in -cassetteduplicator.

TAPELowest prices on Scotch

207 and Agfa PEM368

IMMEDIATE DELIVERYFINANCE AVAILABLEPrices exclude VAT

1-7 Harewood Avenue,Marylebone Road, London NW1.Tel: 01-485 6162/7833.Telex: 21879.

Please

TEAC

Name.

Address

The 805in use Itam delivers....Worldwide: The Ram 805 8 channel recorder gets

UK you into the Big league FAST. Itprovides a new area of penetration

Turkey for budget studios.

USAFacilities like trackbouncing, variable

s. Africa speed and silent

Philippines4e'vderroypsitnusd"i aD1 to

Switzerland THHEOCBLOIEONK-TS

Denmark YOUR STUDIO

Greece

r Sweden

HollandBelgiumGermany

France

-;AustraliaFinland.

TIME. Get the factsfrom our sales deskwho will fill you in onthe details and setup a finance dealwith your trade-in Portable £1790 f VATright now. Console £193° j VAT

....the rest onlypromise

Immediate Delivery1-7 Harewood Avenue, Marylebone Road, London NW1. Tel: 01-485 6162/7833. Telex: 21879.

ASSOCIATION OF PROFESSIONAL RECORDING STUDIOS

PROGRAMME 1977

CANNES MIDEM 21-27 JANUARThe annual get-together of 5000-6000 people from all over theworld interested in every aspect of recording and publishingof music.At MIDEM APRS will issue a 40 -page Catalogue of its membersto advertise recording facilities in Great Britain.

PARIS 56thAES

CONVENTION 1-4 MARCNineteen British manufacturers are exhibiting as part of thisConvention in a joint British Overseas Trade Board 'Associationof Professional Recording Studios venture.APRS will issue a Catalogue.

LONDON APRS 77 15-16-17 JUN10th Annual Exhibition of Professional Recording Equipmentat Connaught Rooms, London.(During the Centenary of the invention of the recording of sound.)

GUILDFORD 4th ENGINEERS COURSE SEPTEMBESURREY. U.K. A course of lectures, demonstrations and discussions for

studio engineers, to exchange views on techniques and problemsof common interest.

HOME COUNTIESOR LONDON

MANAGEMENT AUTUMA weekend course for studio managers on studio management.

For further information on above, or for application for membership (studio, manufacturer or educationwrite to The Secretary, APRS, 23 Chestnut Avenue, Chorleywood,Herts WD3 4HA, United Kingdom.


A NEW STANDARD OFEXCELLENCE

Harrison 4032 and 3232Master Recording Consoles

NO COMPROMISE

HarrisonInformation, sales and service are available through our selected professional audio distributors:

AUSTRIA,SWITZERLAND AND Studer International AG (Switzerland)

EASTERN EUROPE: Tel (056) 26 87 35. Telex 53682

BENELUX: Heijnen B. V. (Netherlands)Tel (08851) 1956 Telex 48039

CANADA: Studer Revox Canada Ltd.Tel: (416) 423-2831 Telex 06-23310

DENMARK: Quali-fi A/STel. (01) 631711. Telex 16527

FAR EAST: Studer-Revox Hong Kong Ltd.(except Japan) Tel: 5-278571 Telex 84640

FINLAND: Into OYTel: (90) 171123. Telex 121836

FRANCE: Studer FranceTel 533 58 58 Telex 204744

GERMANY: Franz Vertriebsgesellschaft mbH.Elektronik, Mess-und Tonstudiotechnik (EMT)Tel (07825) 512 Telex 754319

GREECE Electronica 0 ETel: 36190% Telex 214888

ITALY: Audio Products InternationalTel (02) 27 38 96 Telex 32402

JAPAN: Shindenshi Manufacturing Corp.Tel 03-460-6052

MEXICO: Ingenieros en Electronica Asociados S.A. de C VTel 5-20-91-34 y 5-20-45-91. Telex 1775756

SPAIN: Neotecnica, s a e.Tel 242-0900. Telex 22099

UNITED KINGDOM: Scenic Sounds EquipmentTel: (01) 935-0141. Telex 27939

FACTORY: Harrison SystemsPost Office Box 22964Nashville, Tennessee 37202

Tel (615) 834-1184 Telex 555133

EXPORT AGENT: Audio Systems International146 North Orange DriveLos Angeles, California 90036Tel (213) 933-2210 Telex 698645 or 555133

TEAC 3340S and 2340SX.The best 4 -channel recordersavailable, ideal for demosand multitracking.

REVOX A77 mk. 4. Availablestandard, high speed,varispeed, selsync.

We stock all Nakamichi professionalcassette recorders.

Tascam 80-8 andModels 2, 3, 5 Mixers.

The excellentBrenell range includingthe Mini 8 1" machine.

Complete range of Allen & Heathmixers including the famousMinimixers, Quasi's and Popmixers.

76 Lyndhurst Gardens, Finchley N3Telephone 01-346 4469

Complete range of Tannoy speakers ex -stock.

Leading Equipment suppliers to professional and home recording studios.

1:1:11::Lekl'eCLeieleile:Le1W

Export service avail&


We Capture ANY Sound!

AKG -the right microphonefor every application

The cheering of the spectators at the Olympic Games.The roaring of a formula I racing car. The singing of the

greatest singers in the world. The capturing of thoseprecious moments in family life, on tape. Wherever crystal

clear reproducing or recording is required you will find AKG,for every application there is a specially designed

AKG microphone. However high your quality requirementsmay be - AKG can exceed them.

Please send me by return, informations about

0 sound reinforcement 0 studio microphones

0 musicians microphones 0 headphones

Name

Address

Country >Please recommend the best mic for my particular application <

0

182/4 Campden Hill Road Kensington AKG Equipment Ltd. London W8 7AS Telephone 01.229.3695

AKG EQUIPMENT LTD. 182/84 Campden Hill Road Kensington London W 8 7AS Telephone 01.229.3695AUSTRIA, AKG Akustische and Kino-Gerate Ges.m.b.H. Wien, Brunhildengasse 1. A-1150 Wien. TF: (0222) 92 16 47 BELGIUM, Radelco P.V.B.A Italielei 179, Antwerpen,TF: 03-337 880 CANADA. PHILIPS Audio -Video Systems. 200 Consumers Road. Suite 105. Willowdale. Ontario M2J 4R4, Canada, TF: 494.1453 - DENMARK. S.C. Sound,Brondbyostervej 84, Dk-2650 Hvidovre, TF: 01-471222 FINLAND. Nores 8 Co. 07. Fabianinkatu 32. Helsinki 10. TF: 13360 FRANCE, Reditec, 27ter, Rue du Progres,F-93107 Montreal, TF: 3282580 GERMANY. Akustische and Kinogerate Gesellschaft m.b.H., BodenseestraBe 226-230, D-8 Munchen 60, TF: 089/870011 ITALY,M. Casale Bauer, Via IV Noyembre N 6-8, 40057 C.adriano di Granarolo. P.O.Box CP 753, 40100 Bologna, TF: 061/766648 NETHERLANDS, Rema Electronics. Isarweg 6,,Amsterdam, P.O.Box 8501, 1015 Sloterdijk, TF: 114959 NORWAY, J. M. Feiring A/S, P.O.Box 101 - Bryn, Oslo 6, TF: (02) 686360 SPAIN. Neotecnica S.A.E., Marques deUrquijo. 44, Madrid - 8, TF: 248 96 02 SWEDEN, Harry Thellmod AB, Hornsgatan 89, S-11721 Stockholm, TF: 08-680745 SWITZERLAND, Audio Electronic AG,LohwisstraBe 24, CH -8123 Ebmatingen, TF: 97 14 70 USA, PHILIPS Audio -Video Systems Corp., 91 McKee Drive, Mahwah, New. Jersey 07430, TF: 201-529-5900

!WW1Sonifex cart machineSonifex has brought out a newcartridge machine accommodatingA size cartridges. The machine,QFX-500, is equipped with servomotor drive, an air damped sole-noid for quiet operation and mutingin the fast forward (50 cm/s) andstop position. It uses Cannons forthe signal interface.

Equipped with primary cue faci-lities, it incorporates an equalisedcue output to enable operationwith external secondary and ter-tiary cue apparatus. Extract frommanufacturer's specification:Cart size: NAB A.Equalisation: NAB or CCIR (toorder).

Teach injsell outAt a recent symposium held at theMelodia Studios in Moscow, 3M,Sondor, White, Cadac, dbx,Master -Room et alia demon-strated their European andAmerican technology to more than200 senior engineers working withinthe Soviet Broadcasting, Film andRecording Industries.

At the close of the seminar, theState Committee placed orders for3M 79 machines, dbx noisereduction, Master -Room reverbunits and White Instrument prod-ucts proving that capitalism isn'tdead.

Rotary potPenny and Giles potentiometershave introduced a single axis potwith 240° turn. The manufacturerclaims a combination of precisionand reliability in adverse operatingconditions. It offers a self centringmechanism stated to produce a restposition accuracy better than 0.5%between wiper and centre tap.

Frequency response: 40 to 15k Hz±2 dB.Stereo phase: 45° at 100 Hz and15k Hz reference 0° at 1 kHz.Distortion : 2 % thd ref +8 dBabove standard tape reference(NAB 19 cm/s 320 n Whim one sup-poses-Tec Ed).Wow and flutter: less than 0.15Ms.Start/stop time: less than 100 ms.Dimensions: 76 x 215 x 290 mm.Sonifex Sound Equipment, 15College Street, Irthlingborough,Wellingborough, Northants NN9STU.Phone: 0933-650700.

Units can be supplied in fundamen-tal resistance values between 250ohms and 30k ohms; further, theycan be fitted with or withoutadditional taps including centretap. Penny and Giles Ltd,Mudeford, Christchurch, DorsetBH23 4AT. Phone: 042 52-71511.Canada: Aviation Electric Ltd,PO Box 2140, Station 0, MontrealH4L 4XH. Phone: (514) 744 2811.

ModulesAn Australian Company, StudioElectronics Pty Ltd, has enteredinto the encapsulated/pcb modulemarket with a series of deviceswhich claim a very high standardof electrical performance:

1) SEO-1 Operational Amplifier.This offers a quoted 100kHz power bandwidth delivering+20 dBm into 100 ohms. Dis-tortion stated as less than 0.1 %thd. Noise less than 0.7 tiNequivalent input 20 to 20k Hz.Price $40.2) VCA-1 Voltage Controlled


Attenuator. Claims 100 dBdynamic range; tracks within 2dB between any two units over60 dB. Distortion quoted as lessthan 0.01 % at +4 dBm. Price$36.50.3) 130 Peak Programme Meter.Led column scale reads from -30to +6 dBm. Integration timequoted as 10 ms. Price $140.4) 377 Headphone Amplifier.Produces 2W at 0.1 % thd.

Studio Electronics Pty Ltd, POBox 1055, Burwood North 2134,Australia.

Midem 77Midem, the acronym for MarcheInternational du Disque et deI'Edition Musicale, will be heldfrom January 11 to 21, 1977 at thetraditional Cannes venue. To pro-vide space for an additional 105exhibition booths, the covered carpark has been turned into extradisplay space. The total numberof stands will exceed 1090; how-ever, nobody can state with anydegree of certainty whether therewill be any facilities for the derigeur crop of Rolls-Royces thatthe event attracts.

There will be an internationalmeeting of lawyers at the HotelMajestic which will take place onthe 20 and 21. Subjects for dis-cussion include the legal problemsset by `videogrammes' whateverthey are and 'the part played byjurists in the drafting of contractand sub contract clauses'. Quotingthe Marx Bros, it should proveconclusively that 'there ain't noSanity Clause'.

Harrison-survey omissionInadvertently, we omitted Harrisonfrom our survey of recording con-

soles (January STUDIO SotBelatedly, here are a few facts athis company's productsshould have been included:

This company's desks are ton an input/output channel vis mode selectable from abutton group adjacent tochannel fader. The basic capais either 40/32 or 32/32; the syorganisation relies on use ofstate switching matrices to elecoperational status of the vachannels from four options ccponding to the usual mic/macmonitor etc.

The channel panning facilitieextensive with normal odd/evesfor the routing; each duincorporates full quad positicwith quad mix busses for siquent mixdown.

Vca faders allow up to ninegroups together with a read/vupdate control when usedautomation. The eq facilitiestwo -band parametric with hilo pass.

For further details see MultiReview (January 77, p68) ancAPRS report (August 76, p54;Harrison Systems, PO Box Z.Nashville, Tenn 37202, IPhone: (615) 834 1184.UK: Scenic Sounds Equipr27/31 Bryanston Street, Lo:WIH 7AB. Phone: 01-935 I

Tannoy change of addressTannoy has moved locatioiBuckinghamshire followingaddition of Harman KardonOrtofon products for disttion by the group throughouUK. Tannoy Rentals Ltdremain at West Norwood.

The new address is Tannoy Iucts Ltd, St John's Road, TGreen, High Wycombe, BPhone: 049 481-5221.

The new HarrisCB -1201professional transcription turntable-a new broadcast product

once is enough!

Miter is pure and clear. Still, if we look at a leaf which ispartially submerged in it, the leaf looks distorted. It is sur-prising how easy it is to introduce distortion, even by thesimplest type of operation on Nye Rill thing. The bent leaf doesn'treally bother us very much, but when distortion in sound resultsfrom the use of equipment, this bothers us a lot!

Some OTARI specialists spend most of their day making surethat the equipment that we produce has the lowest possiblewow and flutter, and the highest possible S/N ratio. Naturally,these are not the only features which create the top performanceof OTARI products, but they reflect the care that results in atotally balanced OTARI product, and better service.

Trust through experience- one encounterwith OTARI equipment and from then on,You will trust the OTARI name.

MX -5050-2S MX -7308

ENGINE!OTARI CORPORATION: 981 Industrial Road, San Carlos, California 94070, U.S.A. Phone: California 415-593.1648 Telex No. 259103764890 OTARICORP SCLS

OTARI ELECTRIC CO., LTD. 4.29-18, Minami Ogikubo, Suginami-ku, Tokyo, 167 Japan Phone: (03) 333-9631 Cable: OTARIDENKI TOKYO Telex: J26604 OTRDENKI

21

Itaft 4117.1ara v "Ne9M196116P.1.44-0mmisa

NEWS

Delay price reductionsFWO Bauch has announced pricereductions of between 10 and 15on all Lexicon Digital Delayequipment including vco modulesand the new stereo version of the102 range.

The new prices mean that a basicdelay system with 160 ms ofdelay and two outputs now costs£2890.FWO Bauch Ltd, 49 TheobaldStreet, Borehamwood, Herts WD64RZ. Phone: 01-953 0091.

Level vduLink Electronics has produced aunit for translating audio inputs ofup to 32 channels into a singlesignal enabling colour or mono-chrome tv monitors to display levelinformation in bar form. Desig-nated type 426, it uses a pin boardmatrix to control the size of dis-play; when showing less than 32audio inputs, unused bars can bedeleted from the display withremaining bars increased in widthto enable greater clarity.

The unit is supplied with iden-tifying buttons for location adja-cent to the channel faders whichmodify the relevant bar in eithercolour or brightness for quickidentification. When a channel is

a similar displaychange occurs. Switched ballisticssimulate either vu or ppm charac-teristics.Link Electronics Ltd, North Way,Andover, Hants SPIO 5AJ. Phone:0264-61345.

New range of mixersGelf Electronics Ltd is a relativelynew company engaged in the pro-duction of studio and allied gear.Among its products are a 16/6monitor mixer, a studio desk witheight subgroups, full channel eq,P & G faders, XLRs etc; an autophasing unit, electronic phaserincorporating an internal controloscillator as well as an envelopephaser, and an active crossover.The active crossover offers fixedfrequency four section split com-bined with stereo operation.Gelf Electronics Ltd, 38 HomeClose, Bletchley, Milton KeynesMK3 6JE. Phone: 0908-77503.

Low cost StuderStuder has brought out a masterrecorder,the A80IRC, which offers a


-5-7-10- 13-16-19

22-25-3a

- 40- 45- 50- 55

. 2

Ode-1

-5-7

10-15

The new range of Miniflux led meters. Available in several ranges ofresolution, they are said to comply with DIN, IEC or BS 4297 standards

price reduction of about £800 on theA80IR stereo machine. Developedfrom the A81 machines suppliedto the German Broadcasting Cor-poration, the new machines incor-porate a new tape transport con-trol, and an electronic tape timer isstandard. The manufacturer claimsthat the price reduction has beenachieved through rationalisationof production techniques and test-ing procedure.Studer International AG, Althard-strasse 150, CH -8105 Regensdorf,Switzerland. UK: FWO Bauch, 49Theobald Street, Borehamwood,Herts WD6 4RZ. Phone: 01 9530091.

Studer addressThe Swiss Studer organisation haschanged address to new premiseseffective since December 15: StuderInternational AG, Althardstrasse150, CH -8105 Regensdorf, Swit-zerland.

Didn't they do well ...ALICE-for a major revamp atRadio Clyde, John Lumsden chosevariants of the AM system for thetwo main on -air studios. Thenew mixers, which should beworking in the new year, will be in

Studer low cost A80112C stereomaster machine.

V- V V v II -V V V V ,*. '....

1^, =v141-1, '.41-v '-v1- '-v,

addition to existing Alice productssituated in the music studio andthe ob van. The company hasrecently sold an £8000 desk toCFRW in Winnipeg-`the serviceof high quality music to thePrairies'.NEVE US has also sold a fewmore. An 8038 24 -track has turnedSounds Studio, Hawaii into theonly 24 -track facility in the 50thState. The chances are Hula musicwill never be the same again. Nevehas also supplied an 8068 compactconsole to the Manta Sound Com-pany of Toronto and Les StudiosMarco of Montreal. These are inaddition to the recent installationof the same type of desk at theFour Star Studio Complex at

Nashville-not counting the five

recent broadcast installations scat-tered round the US.HAYDEN LABS say that theyhave sold untold numbers of NagraIS -LT tape recorders-one size

down from the classic 4.2-to theBBC film department. They willbe mostly used for film locationand current affairs work.

Leader availableC. E. Hammond say that they cannow supply, off the shelf, the following Leader instruments:LDC 821 digital frequency cmter, the LAG 120 audio generator,the LMV186A stereo millivolt.meter and the LEM 75 electroniimultimeter.C. E. Hammond & Co Ltd, 105109 Oyster Lane, Byfleet, SurreKT14 7LA.Phone: Byfleet 41131.

Alignment oscillatorBarry Porter, erstwhile designewith Trident, has started his OWcompany, Midnight Audio LtdOne of his first products is ai

instrument designed to simplrroutine lining up of pro tap

recorders.The Alignment Oscillator typ

464 offers:Push button selected 10 frequentoscillator with up to +20 (IRoutput capability. A metering sation which claims to give 2'

accuracy at any attenuator se

ting when reading 0 vu.Duplicated XLRs for oscillate

output and meter input.A sum reading (whatever th

means) for head azimuth aligment. The unit is mains powerand costs £165.

Another Porter -designed Mnight Audio product is an andvoltmeter type 348 for accurate,

24

The NewMaster -Roomr Series

Independently variable seriesavailable with two 1-3 second channels,two 2-4 second channels or one1-3/one 2-4 second channels.

Studio 'B' SeriesSingle channel series with variabledecay plus equalisation. In 1-3 or 2-4second models.

M -R Studio SeriesFixed decay time single input/stereophonic return. Available in 2, 5 and7 second optimised decay timemodels.

Naturally chosen by recording studiosworldwide from Memphis to Moscow.Master -Room Reververation Unitsby MIC MIX Inc., Dallas, Texas.

Sole UK agents :Scenic Sounds Equipment27-31 Bryanston Str., London W1H 7ABPhone : 01-935 0141 Telex : 27 939

France:3M France SA Mincom Div.135 Blvd. Serurier, Paris 19EPhone: 202 8080

Holland:Pieter BollenGeluidstechniekEindhovenPhone: 040 512777

Denmark :Recording Operation Co.Artillerivej 40DK 2300 Copenhageen S.Phone: 01 570 600

Norway:SIV. ING. Benum/Skovvn 22Oslo 2Phone : 02 56 57 53

Sweden:Ing Firma Jan SetterbergKungsgatan 5S411 19 GothenbergPhone : 031 13 02 16

23

NEWS

voltage and frequency measure-ment. It offers an fsd range from150 1..V to 50V in 12 ranges andreads -80 to +30 dB at centrescale. Also it offers direct powerreading to 250W into 8 ohms. The

unit incorporates three filters: 1)20 to 20k Hz. 2) CCIR. 3) DIN Aweighting. The frequency counteris a six digit unit with gate periodsof 0.1, 1 and 10 seconds. The unitcosts £395.Midnight Audio Ltd, PO Box 12,Fleet, Aldershot, Hants GU138EF. Phone: 02514-20143.

Midnight Audio tape machine alignment oscillator

BloodsuckerThis man, the advertisement mana-ger of STUDIO SOUND, was giventhe Dracula Award at the recent

DEAF dinner for being 'the biggestbloodsucker in the industry'. We,the magazine, feel this an awardthat he richly deserves; however,

we should point out that thishas been exacerbated by

an unfortunate medi-cal condition (see

picture).Our

Quantum Audio QM -128 eight bass mixer selling for only $4300

medical correspondent writes: Itis not uncommon for ad managersto suffer pecuniary toxaemia (ItchyPalm), usually concurrent withsymptoms of inflationary paranoia.Classic symptoms include a ten-dency to make rash statements of apromissory nature, while leavingtwo little puncture holes in thewallets of those who have been inclose contact with the subject. The

prognosis isn't very hopeful.Treatment: frequent trans-

fusions from blooddonors.

Quantum deskEach module on the new QM -128has solo, mute, two independentecho sends and two independentcue sends, six frequency eq onthree knobs and switchable 15 dBpadding on the mic amp. Channelfaders are of the conductiveplastic type.

Monitoring can be selected bypushbutton to buss, line or play-back; slate can be put on any of theeight output groups. They alsoincorporate buss metering facilities.

The desk comes in a beige colourwith a textured brown chassis; allcontrol functions are colour codedfor ease of identification. Optionalextras include a patch bay, phan-tom powering and an eight inputexpander. The basic price is$4300 which seems very reason-able.Quantum Audio Labs Inc, 1905Riverside Drive, Glendale, Ca91201, USA. Phone: (213) 841

0970.

noce is yo..COP.1{,011 - MEM

Specialists in Audio Controlequipment for the Broadcast andSound Recording Industries

ft

Stereo compressor/limiters andpower supply in I9in standard rack

TWEED AUDIO00.

911101

If you recuirosuperb cuclity,too oerformc-yorovon rclicbilitycnc electronicscesigpcc withmusic in mine,write or 'onone,

TWEED AUDIOELECTRONICS

ROSEWOOD INDUSTRIAL ESTATE, KELSO, ROXBURGHSHIRESCOTLAND TELEPHONE 2983 STD 05732


Next to your Oscilloscope, perhaps the mostpowerful test instrument you can own

(A., 0(4csc,ON 0 0 C) c (,)

*10-

((4((((6(((/4.#. 1%6

The Amber model 4400 MultipurposeAudio Test Set-a powerful, comprehen-sive test instrument combining in a singlepackage almost all the test and measure-ment facilities needed for professionalaudio testing.

Use it to plot the frequency response of atape recorder, a microphone or a speaker.Look at the slope characteristics of a filteror equalizer. Equalize a monitor system,measure the crosstalk in a mixing desk,check the gain of an cmplifier or plot thephase response of a preamp -the 4400will give you a fast, concise and accuratepicture of the performance of a piece ofequipment.

In North America

Amber Electro Design Limited1064 Golf RoadMontreal, Canada H3E 1H4Tel: (514)769-2739

Amber model 4400 Multipurpose Audio Test Set.UK list less than 42200. Oscilloscope not included.

It incorporates a function generator withlow sine wave distorsion, 10 octave logsweeper, tone burst generator, noise gen-erator and high power (over + 30 dBm)output amplifier. It has an autorangingdigital dBm meter with over 150 dBmeasurement range, a frequency counter,a multifunction filter that can be used as aspectrum analyser and four digital mem-ories that give you X Y frequency andphase response plots on any non -storageoscilloscope.

A fantastic time saver both in new productdevelopment and regulor equipmentmaintenance. If you're involved in pro-fessional audio-acoustics, studio equip-ment, tape recorder maintenancewhatever-find out what the incredibleAmber 4400 can do for you.

UK Representative

Scenic Sounds Equipment27-31 Bryanston StreetLondon W1H 7AB EnglandTel: 01-935 0141Telex: 27 939

Elsewhere

Gotham Export Corporation741 Washington StreetNew York New York 10014Tel: (212) 741-7411Telex: 12.-9269

25

Monitor equalisation

GEORGE AUGSPURGER *

Third octave analysis can't replace agood pair of ears. However, objectiveanalysis can provide a good startingpoint for subjective discussion.

*Perception Inc

Historical perspectiveELECTRICAL equalisation of loudspeakers has been practised

for more than 40 years. The renowned 1933 stereophonicre-creation of the Philadelphia Orchestra made use of sophisticatedequalisation, and the description of the experiment in the BellLaboratories Record points out that correct equalisation of a givenreproducing system is different for every hall. In the UnitedStates Dr C P Boner later pioneered the use of equalisation in soundreinforcement systems, both for suppression of acoustic feedbackand to achieve natural tonal quality. In the 1940's, Ampex presenteda number of 'live vs recorded' demonstrations and again thereproducing chain was equalised for natural sound quality.

In 1968, Altec's `Acousta-Voicing' process was first used toequalise the response of recording studio monitor speakers. Sincethen, a variety of active and passive equalisers suitable for monitorequalisation has appeared. In US control rooms and mixdownrooms, probably more than 50 per cent make use of some degree ofelectrical equalisation in their monitor chains.

I became interested in equalisation of sound reproducing systemsabout 15 years ago. My early experiments were confined toattenuating one or two bands of frequencies in the mid -bass region,where room coloration is most apparent in typical listening rooms.Later, when 3 -octave analysis and equalisation gear becamegenerally available, I tried to develop techniques to meet the particularrequirements of recording studios.* The following paragraphsrepresent a personal view on the subject, based on experience insome 80 control and mixdown rooms.

Measurement-objective or subjective?Early measurements of acoustical response were made using

swept sinewaves. However, in any enclosed space, normal modesor eigentones are so closely spaced, and sound pressure changesso dramatically with the positions of ear (or microphone) and source,that sinewaves tell us a lot more than we would really like toknow. Some sort of averaging is needed to correspond with oursubjective assessment of tonal balance.

So, warble tones were later used to generate a 'window' offrequencies, usually 10-20 Hz wide. But the technique that hasproved to give the best correlation with listening tests is the use ofbands of noise, nominally 1 -octave wide.

In theory, pink noise can be filtered into 1 -octave bandseither before it is fed to the loudspeaker or after it is pickedup by the measurement microphone. There are practical reasonsfor choosing one or the other (as will be pointed out shortly)but the results should be the same.

Random noise simulates the transient characteristics of typicalprogram material and }-octave bands on standardised centre

*In co-operation with a Canadian associate, these are In the process of beingformalised under the trade name Sonovoice.


frequencies give sufficient detail for most applications withoutintroducing unnecessary complications. The reason for this happystate of affairs is that the critical bands of the human ear arefairly close to +-octave wide. But it is easy to jump tofallacious conclusions from this fact. Some writers imply that youcan do whatever you like within a single band because the earcannot resolve to a finer degree than 1 -octave . . . not true.

In a similar vein, the response curve generated on the screenof a 1 -octave sound analyser is often regarded as Holy Writ. . . it is the frequency response of the system. Some recordingengineers have become so disillusioned after hearing obviousdifferences between systems having identical measured response thatthey dismiss the whole equalisation effort as a fraud.

The fact is that the jr-octave measuring stick is a powerfultool. However, when measuring and equalising sound reproducingsystems, especially recording studio monitor systems, octavenoise bands do have several limitations that cannot be ignored.

1) Because the test signal is derived from random noise, itsspectral content and its level at any frequency or band of frequenciesare both constantly changing. The level of confidence for anyanalysis based on bands of noise is something in the neighbourhoodof ±1 dB. But a trained ear can easily hear differences of 1 dBwhen making an A -B comparison between left and right speakers.

FIG.I PUBLISHED FREE -FIELD CORRECTION CURVES FOR THEB &K 4134 12mm CONDENSER MICROPHONE

.5

dB 0

5

60'RANDOM

90'1k 2k 5k 10k 20k

FREQUENCY NI Hz

A 2 dB uncertainty factor is unacceptable to the recording engineer.The remedy is to give up that fascinating toy, the real-time

analyser.* By driving the system sequentially with -1-octavebands of noise, one can compare the relative levels of left andright speakers not only with the test microphone, but also (radicalsuggestion) by listening. If, as usually happens, there are differences

ain timbre between the two monitor speakers, final balancingcan be done on the basis of subjective response, a single band at atime. This works in spite of the fluctuating nature of the test signalbecause a rapid A -B switch catches it in mid -strike, so to speak.And, by using the ear as a check against the test microphone, one canallow for subtle differences within a single band that do notshow on the plotted response curve.

2) Additional uncertainty is introduced in trying to definethe listening location. Even with the averaging effect of a band offrequencies, the measured sound level in any one band canvary dramatically with small changes in microphone position.The usual response curve derived from a single microphone atthe centre of the console is analogous to what would be heard by aone -eared recording engineer with his head in a clamp.One possible remedy is to move the microphone around in

the general vicinity of mix centre and try to average the readingsobtained. One can sit at the console with a sound level meter inone's lap, for example, and sort of wave it around slowly in a

Most i-octave sound analysers used for monitor testing and equalisationare not true 'real time' devices. However, the distinction is notimportant to this discussion.

circular pattern while noting the variations in level. But this may notbe any better than accepting the limitation of a fixed measuringposition. For one thing, it is not a repeatable test technique. Foranother, waving and watching and mentally recording allows thesubconscious to insist on the figure hoped for rather than theone that would be noted by a truly unbiased observer.

A better technique is to make three or four separate sets ofmeasurements at defined positions and then average the results. Thistakes time, especially when performing equalisation. The threelocations can be better averaged automatically and simultaneously byusing three calibrated microphones and some kind of multiplexingcircuit to average (not mix) their outputs.

3) A third area of uncertainty exists because of the directionalcharacteristics of the measuring microphone and of the ear.With a little caution one can be reasonably certain that the

microphone is responding in random -incidence fashion over most ofthe audible frequency range. A 12 mm microphone such as theB & K 4134 has omnidirectional response up to about 5 kHz. In therange from 5 kHz to 15 kHz random -incidence response andgrazing -incidence response are within 2 dB of each other (fig. 1).However, if a strong directional component approaches the micat an angle of 60° or less a bias of several dB can be introduced.

In comparing curves run with my equipment against thoselogged by others, I find the largest discrepancies in the frequencyrange above 5 kHz. In some cases the differences can be tracedto ignorance of microphone characteristics. (Point a sound level meterat the loudspeaker and simply plot what it indicates.) In otherinstances it does not seem that my array of three 4134 mics isnecessarily any more accurate than the equipment used by the studio.

I am tempted to acquire three 3.13 mm microphones. Thesebeautiful little B & K units are truly omnidirectional up to about20 kHz. That is, they would be omnidirectional if the associatedpreamplifier did not shadow the microphone at its rear. Asalways, nothing in life is perfect.

In any case, a non -directional pick-up pattern does not ensurecorrelation with the directional characteristics of the ear. The differencein perceived loudness between frontally directed and diffuse soundfields is about +3 dB at 1 kHz, -2 dB at 2.5 kHz and more than+4 dB above 8 kHz. In many control rooms the diffuse fieldpredominates at low frequencies, the direct field predominates at highfrequencies, and the two are roughly equal through the mid -range.Since different monitor speakers in different environments willproduce differing ratios of direct -to -reflected sound, the notion ofmeasuring the response of the system is beset with uncertaintieson this basis alone.

Fortunately, from a practical standpoint the important thingis to have a test setup which correlates reasonably well withsubjective evaluation and which allows repeatable measurements tobe made. One learns quickly that, for engineer A in control room B,measured high frequency response should be shelved 1 dB above2 kHz and rolled off at about 3 dB per octave above 5 kHz.Whether this curve represents the 'real' response of the

FIG. 2 SINE WAVE RESPONSE OFCONTROL ROOM MONITOR ASAVERAGED FROM 3 MICROPHONE POSITIONS NEARCONSOLE CENTRE

10dO

li\tt

(\,30 50 100 200

FREQUENCY IN It

a

system is beside the point.4) Finally, using *-octave bands on standard centrefrequencies gives ambiguous readings if the peaks and dips insystem response, as measured with a swept sinewave source,happen to be about }-octave apart. This is exactly what

happens below 200 Hz or so in small rooms.Fig. 2 shows the sinewave response of a control room monitor

as measured at the centre of the console. An array of threemicrophones was used, so that space averaging is already included inthe plot. Note that the lowest peak and following dip are closeto the standard centre frequencies of 31.5 and 4() Hz and, therefore,will also show up on i-octave analysis.

However, the peak at 56 Hz and the dip at 75 Hz fall in the`cracks' between standard }-octave bands. foctave analysis willgive a misleading picture of the true state of affairs in this region.

There are a number of ways in which the resolving power ofour measuring system can be improved in the low frequency range.Sinewave response can be plotted, but this takes a lot of timeto do manually or a lot of money for extra equipment to doautomatically. One might switch to A -octave analysis at lowfrequencies but this increases the difficulty of getting a true levelaverage over a sufficient length of time. Even with -A-octave bandsof noise, signal fluctuations at the lower frequencies require severalseconds of averaging time and make eyeball estimate difficult.

A continuously swept }-octave analysis works reasonably well, butagain is time-consuming and requires additional expensive test gear.

It seems to me that a good compromise between measurementresolution, simplicity and speed is to use sequential sinewave signalsat 11, -octave centres for measurements in small rooms

F IG. 3 THE CURVE OF F G 2 RE -PLOTTED FROM it. OCTAVE SINE WAVESIGNALS BELOW 200 Hz

5

dB

10

15

I

31 s El 1Y. 125 lit /00 35 000 Ste 6J0 8)0 1KFREQUENCY IN Hz

below 200 or 250 Hz. Fig. 3 shows what happens when the responsecurve of fig. 2 is replotted in the new format.

Acoustical vs electrical monitor equalisationHaving measured the response of a monitor loudspeaker with

some degree of accuracy, the question arises: to equalise or not toequalise? It would seem that if the loudspeaker is inherentlyflat and if the listening room is correctly designed, measured responseshould be uniform and no further adjustments should be required.

But a control room is rarely an ideal listening room. It istoo small. As a result, the normal modes of the room produceaudible peaks and dips at low frequencies, as we have seen. To makematters worse, the listening location is necessarily near the centreof the room, the worst possible location from the standpointof low frequency response.

In those cases where a room can be designed from the verybeginning with plenty of adjoining space for low frequencyabsorption, smooth bass response can be realised over a fairly largelistening area. In effect, one builds a visually small room insidean acoustically large shell.

More often than not, however, even though we use all thetricks learned from previous experience, and although we spend twoor three days experimenting with reflective and absorptive surfaces,the best we can manage is smooth response except for, say, ageneral hump in the 125 Hz region and excessive roll -off below50 Hz, as in fig. 4.

Faced with this common situation it makes sense to introducevery simple electrical equalisation even if the client does not want afully equalised monitor system. The equalisation required forsuch trimming has gentle slopes with correspondingly little phaseshift. Even the most vehement anti-equalisationalist accepts a few dBof boost at 40 Hz and a few dB of attenuation at 125 Hz oncehe hears the improvement in listening quality. 28

27

MONITOR EQUALISATION

If such results can be achieved with only minimal equalisation,and if one believes as 1 do that the best equalisation is the leastequalisation, how is it possible to justify the use of completeoctave banks of equalisers, with separate filters for each bandfrom 40 Hz to 16 kHz and 10 dB of boost and cut available ateach centre frequency? . . . Easy.

The value of complete 3 -octave equalisation lies not somuch in its ability to compensate for gross problems in monitorresponse (which is never really satisfactory anyway) as the precisionwith which more subtle changes can be achieved. With today'scomplex multitrack mixes it takes only a dB or two in a given bandof frequencies to change the balance between tracks. Only with fullI -octave capability is it possible to arrive at and maintain thebest response curve for comfortable mixdown in a particular situation.

And only with complete I -octave equalisation is it possibleto achieve near -identical response from all of the monitorspeakers in the control room. Even though many filters maybe set at 0 during the process of equalisation, they may be needed twoor three months later when the monitors have drifted slightlyfrom their original performance characteristics; I don't knowwhy loudspeakers should drift, but the level of stability for a typicalmonitor system is about that of a grand piano.

Let me emphasise that equalisation will not allow you to makea Tannoy sound like a JBL; it will not fool your ears into believingthat large, dead control room A is small, bright control room B.It will not circumvent the basic limitations of the electronics,the loudspeakers and the room.

Ar B &K 4134 HYPOTHETICAL 1IU OCTAVE REPONSE OFA GOODMONITOR SPEAKER IN A WELL -DESIGNED CONTROL ROOM

.10

dB0

-10

100 1000

FREQUENCY IN Hz

10t

.1

FIG.5 TYPICAL FILTER CHARACTERISTICS. UPPER CURVE: SINGLEFILTER SET FOR 8dB BOOST. LOWER CURVE : SAME FILTER SETAT 0 WITH NEIGHBOURING FILTERS SET FOR 8dB CUT

.5

5

FREQUENCY IN Hz

2

Properly done, monitor equalisation will allow you to mixwith confidence, knowing that the balance between tracks and thespecial effects created at the console are accurately portrayedby the control room monitors.

Phase shift and ringing ...?The filters used for sound system equalisation usually consist

of single LC sections or their active equivalents. They are simpleresonators with maximum phase of ±90°. As used for speakerequalisation, phase shift seldom exceeds 45°.

Moreover, such resonators are not only minimum -phase devices


but their response combines in minimum -phase fashion. Byadjusting individual filters in such a way that the resulting sinewaveresponse curve is smooth and gentle, results are exactly the sameas if only a few much broader filters had been used. The mistakemade by many technicians is set to one knob at -6 and the nextat -10 and the next at +8 in an effort to get a 'flat' response curve. Theresulting curve may look flat but it sounds terrible because of thenarrow peaks and notches in the electrical response of the equalisers.

Some people believe that I -octave bands should never beboosted 'because boost filters ring'. This is nonsense based on agerm of truth.

In most filter sets having boost and cut capability the functionsare reciprocal. At extreme settings the bandwidth is much narrowerthan when only a little boost or cut is inserted. If an isolatedfilter is set for 8 or 10 dB of boost (again in a misguided effort to makethe analyser display look pretty) the band of frequencies near thecentre is narrow enough to be heard as a definite tonality.

If filters are used only in the cut mode there is a built-insafeguard against this mistake (see fig. 5). To make use of theadded flexibility of boost/cut filters without running into trouble, onesimply remembers not to boost any single control more than3 or 4 dB above the settings of its neighbours.

A more insidious problem can be encountered when filters ineither the boost or the cut mode are pushed beyond the range in whichtheir skirts combine smoothly. The amount of overlap betweenfilters at various settings is different for different products. Mostprofessional devices provide a range of about 8 dB of cut orboost with less than 1 dB of ripple between adjacent filters. Beyondthis point the result is a comb filter instead of a smooth equalisationcurve. Why then do the manufacturers provide 10 or 12 dB ofboost and cut at the centre frequencies? Because 12 soundsbigger than eight.

New hardware for monitor equalisation appears every week.It is probably possible to buy an equaliser that introduces noise anddistortion and makes the monitors sound worse no matter whatits settings, but the same is true for any piece of electronic gear. Aprofessional -quality filter set built by a reputable manufacturerwill introduce no more noise and distortion than a line amplifier.With all filters set at zero it is a line amp and should perform as such.

And there are people who believe that only active filter circuitsshould be used for monitor equalisation because `passive. circuits haveinductors and inductors ring'. I would have more sympathy forthis common belief about inductors had I not discovered thatthe ringing observed in some low frequency passive filters originatedin the capacitors! Just as inductors have distributed capacitanceso can capacitors have appreciable inductance. Occasionally onefinds capacitors in the 2-10 ti.F. range which have sufficientinductance to develop self -resonance below 500 kHz. If such acapacitor is then paralleled with an inductor, two resonancefrequencies can be produced. In the case that brought this effect tolight, parallel LCR filters had been used in a control room toboost the 40-80 Hz region. The studio maintenance engineer calledmy attention to the fact that when the filters were inserted, highfrequency ringing could be observed on squarewaves. The ringingwas traced to a peak in the 60 kHz region, and this was foundto be caused by a particular batch of Mylar capacitors. The moral is:never trust anything until you have checked it.

Given a choice between an LC resonator and its activeequivalent, I would choose the passive circuit simply because it issimpler, quieter and more reliable. The fact is that the top-qualityequalisers made by White Instruments, UREI and Altec all usepassive LC sections suitably buffered by active amplifier stages.

Finally, there is the stubborn recording engineer who listensto all of the preceding arguments but still does not believe inmonitor equalisation because he has heard equalised systemsthat sounded better with the equalisation switched out. Well,certainly. I have heard pianos that sounded better before an inepttuner started tinkering with them. The fault lies in the practitioner,not in the concept of tuning.

To sum up, it seems to me that monitor equalisation has valuefor the recording engineer only to the degree that it makes hisjob easier. Its purpose is to provide a more reliable sonic standard irthe mixdown room. In my experience, the acceptance of equalisedmonitor systems by many of the most critical engineers in therecording industry has already established the validity ofequalisation as a powerful tool for the studio.

INTRODUCING A NEWTAPE DECK FROM A

COMPANY THATNEEDSNO INTRODUCTION.

Besides the standard 1 inch 8 track yousee here, there's a :11 inch 8 track and a 2 inch16 and a 24 track.

Their features include full solenoidtransport functions. Full sync facilities. Fullmodular electronics. Silent drop -ins. Instantstart cue. N.A.B. and C.C.I.R. equalisation.

See and hear it at our demo studio.Pembroke House, Campsbourne Road,Hornsey, London N8.

Where you can also take the opportunityto look over the Allen & Heath Mod II mixer.It's offered with the tape deck in a uniquelypriced package deal.

Or for more information call Andrew Stirling 340 3291.

WE CARE FOR OUR REVOXES-WHY NOT LET US CARE FOR YOURS?We can do anything you can dream up for the A77 within reason, and withoutdetriment to the normal performance of the A77, such as:I Any speed from 30 i.p.s. down to ft i.p.s. without any of the usual problems.2 Improving specifications to the most amazing standards for the professional

user.

3 Pause control.

4 Balanced line mic inputs with or without phantom feed up to 21 volts.5 Cannon input and output.6 RAPID SERVICE.

WE PROVIDE IMMEDIATE SERVICE TO THOSE WHO URGENTLY REQUIRETHEIR REVOKES.

Radio Recordings Tel. No. 01-586 0064WE CAN SUPPLY A RESULT SHEET ON REQUEST FOR ANY MACHINEWE HAVE REPAIRED OR MODIFIED.

8 TRACK AND 16 TRACK RECORDERSOn half -inch or one inch tape. Custom built, withprofessional specification for studio use.Non -Automatic 2 head+-inch, 8 track1 -inch, 8 track1 -inch, 16 track ..All prices plus 8% VATAutomatic remote decks £120 extra3 head systems available

Contact Steve Wadey-0634-76117

£1250£1280£1950

NEW PRODUCTS

STEREO N.A.B. CARTRIDGE PLAYER

Q-FX500 A NEW COMPACT, HIGHPERFORMANCE EQUIPMENT

This versatile equipment has all the features expected by the broadcastingindustry.OUTPUTS. Independent stereo outputs at cannon connectors with full remotefacilities, including equalised cue amplifier output.SERVO motor drive with extremely stable running speed AND ...FAST forward mode with interlocked switching.MUTING in stop and fast forward condition.QUICK START aid damped solenoid with adjustable damping provides a rapid,quiet start.CLEAR cartridge loading area with matching ready indicator, for fast simpleoperation.The low noise, high performance amplifiers and logic systems are complementedby the use of Nortronics professional grade heads.ASK FOR A DATA SHEET.If you like the spec. you will love the price.

S 5000 VARISPEED MONO CARTRIDGE PLAYERA compact monophonic player with SERVO motor drive, AIR DAMPED SOLEN-OID, professional grade heads and FEATURING . . . switched VARISPEED orNORMAL operation.NAB cartridge players GO VARISPEED ... a first by SONIFEX.

SONIFEX LEADERS IN BRITISH CARTRIDGE EQUIPMENT15 COLLEGE STREET, IRTHLINGBOROUGH, NORTHANTS

Telephone: WELLINGBOROUGH 0933-650700

29

Survey: test equipment

Clearly it would be impossibleto include full details of allequipment from everymanufacturer. The followingsurvey comprises an abbreviateddirectory of currently availabletest and calibration hardware ona manufacturer by manufacturerbasis.

ADVANCED ELECTRONICSA E Corporation, 65 Wellesly Avenue, Needham,Mass 02194, USA.Phone: (617) 449 3142.

ProductsFUNCTION GENERATORSFeatures: available in either kit or assembled form.1 Hz to 1 MHz, sine, square or triangle. $124 built.

ALICEAlice Stancoil Ltd, Alexandra Road, Windsor,Berks.Phone: Windsor 51056. Telex: 849323.

ProductsNOISE MEASURING SETSFeatures: ppm with calibrated amplifier and CCIR468 filter, intended for noise measurement in accord-ance with the IBA code of practice. £420.

AMBERAmber Electro Design Ltd, 1064 Chemin du Golf,Montreal, Quebec, Canada H3E 1H4.Phone: (514) 7692739.Export agent: Gotham Export Corporation, 741Washington Street, New York, 10014, USA.Phone: (212) 741 7411.UK agent: Scenic Sounds Equipment, 27/31 Bryan -

Amber 4550 spectrum analyser


ston Street, London W1H 7AB.Phone: 01-935 0141.

ProductsAUDIO TEST SETSFeatures: multipurpose instrument (see review p60).SPECTRUM ANALYSERS

B & KBruel & Kjaer A!S, Naerum, Denmark.Phone: 02 80 05 00. Telex: 37316.US agent: B & K Instruments Inc, 5111 W 164th St,Cleveland, Ohio 44142.Phone: (216) 267 4800. Telex: 810421.UK agents: B & K Laboratories Ltd, Cross LancesRoad, Hounslow, Middlesex.Phone: 01-570 7774. Telex: 934150.

ProductsACOUSTIC STANDING WAVE MEASUREMENTBEAT FREQUENCY OSCILLATORSDISTORTION ANALYSERSFILTERSFREQUENCY RESPONSE MEASUREMENTGATING SYSTEMSIMPULSE RESPONSE TESTINGINSTRUMENTATION AMPLIFIERSINTERMODULATION DISTORTION ANALYSERSLEVEL RECORDERSMEASURING MICROPHONESMICROPHONE CALIBRATION GEARNARROW BAND ANALYSERSNOISE ANALYSERSNOISE GENERATORSOSCILLATORSPHASE METERSPOWER METERSPO TELEPHONE TEST SETSPSOPHOMETERSREAL TIME ANALYSERSSINE RANDOM GENERATORSSOUND SOURCESSPECTRUM ANALYSERSVOLTMETERS

B & K digital frequencyanalyser 2131

II -Ii

t. INF

COURTCourt Acoustics, 50 Dennington ParkWest Hampstead, London NW6.Phone: 01-435 0532.

ProductsSPECTRUM ANALYSERS

Road,

Features: 29 x 11 matrix of led indicators on stain.and ISO centres from 28 to 20k Hz. Particularsuited to disc cutting applications.

Court Acoustics real time audiospectrum analyser

DANAIncluding distribution for CUSHMAN, EXACand EIP.Dana Labs Inc, 2401 Campus Drive, Irvine, C02664, USA.UK agent: Dana Electronics Ltd, Collingdon Stre(Luton, Beds.Phone: 0582-24236.

ProductsCOUNTERSFUNCTION GENERATORSMILLIVOLTMETERSMULTIMETERSSWEEP GENERATORSSYNTHESISED GENERATORSWAVEFORM GENERATORS

DYMARDymar Electronics Ltd, Colonial Way, Radl(Road, Watford, Herts WD2 4LA.Phone: Watford 37321. Telex: 923035.

ProductsAUDIO POWER METERSAUDIO SIGNAL GENERATORSCOUNTERSDISTORTION FACTOR METERSRF GENERATORSSSB TEST GEARWAVE ANALYSERS

FARNELLFarnell Instruments Ltd, Sandbeck IN(Wetherby, Yorkshire.Phone: 0937-3541. Telex : 557294.Overseas agents: in most countries.

ProductsATTENUATORSAUDIO OSCILLATORSFUNCTION GENERATORSMILLIVOLTMETERSMODULATION METERSOSCILLOSCOPES

SURVEY: TEST EQUIPMENT

SIGNAL GENERATORSSWEEP GENERATORSSYNTHESISED SINE GENERATORS

HEWLETT-PACKARDHewlett-Packard Co, 1501 Page Mill Road, PaloAlto, Ca 94304, USA.Phone: (415) 493 1501. Telex: 348461.UK agent: Hewlett-Packard Ltd, King Street Lane,Winnersh, Wokingham, Berks RG11 5AR.Phone: 0734-784774. Telex: 847178.

ProductsDISTORTION ANALYSERSFeatures: manual and auto null.FOURIER ANALYSERSFeatures: 80 dB range of amplitude and phaseresolution for extrapolation of the transfer function.FUNCTION GENERATORSGROUP DELAY MEASUREMENTNETWORK ANALYSERSOSCILLATORSFeatures: synthesised, phase locked and low dis-tortion types available.PO LINE INVESTIGATION EQUIPMENTSIGNAL GENERATORSSPECTRUM ANALYSERSFeatures: H -P manufactures real time equipmentsuitable for use between low Hz and 40 GHz.SWEEP GENERATORSWAVE ANALYSERSFeatures: portable and rack mounting instrumentsavailable for both of and rf.

LEADERUK agent: C E Hammond & Co Ltd. See SoundTechnology.

ProductsAUDIO GENERATORSFeatures: 10 Hz to 1 MHz. Facilities for externalsynchronisation.FREQUENCY COUNTERSMILLIVOLTMETERSMULTIMETERS

LEVELLLevel! Electronics Ltd, Moxon Street, Barnet,Herts EN5 5SD.Phone : 01-449 5028.

ProductsAC VOLTMETERSINSTRUMENTATION AMPLIFIERSMULTIMETERS

MARCONIMarconi Instruments Ltd, Longacres, St Albans,Herts AL4 OJN.Phone: St Albans 59292. Telex: 23350.

ProductsATTENUATORSDISTORTION ANALYSERSFREQUENCY METERSMILLIVOLTMETERSMODULATION INDEX METERSOSCILLATORSPOWER METERSSIGNAL GENERATORSSPECTRUM ANALYSERSSWEEP GENERATORS

TV TEST EQUIPMENTWHITE NOISE TEST SETS

Marconi TF 2370110 MHz spectrum analyser

3MMincom Division, 3M Company, 3M Center,Saint Paul, Minnesota 55101, USA.UK: Mincom Division, 3M United Kingdom Ltd,Whitley Works, Whitley Gardens, Southall, Middx.Phone: 01-574 5929.

ProductsTEST SETFeatures: the seven integrated functions includetracking sine and square oscillators, frequencycounter, wave analyser and a millivoltmeter.WOW AND FLUTTER METERWAVE ANALYSERFeatures: low frequency unit specifically designedfor flutter analysis.

NOMBREXNombrex Ltd, Pound Place, Wolborough Street,Newton Abbot, Devon.Phone : 0626-68297.

ProductsANALOGUE AF FREQUENCY METERSSIGNAL GENERATORS AF/RF

PHILIPSPye Unicam Ltd, York Street, Cambridge CB12PX.Phone : 0223-58866. Telex : 817331.

ProductsAM/FM SIGNAL GENERATORSFUNCTION GENERATORSLF SYNTHESISERSMULTIMETERSOSCILLOSCOPESSINE/SQUARE GENERATORS 32

Amati,Batista,Bechstein...

. . . SME: a worthy companion for theworld's great instrument -makers. The bestreproduction of music, either by electronicor accoustic means, requires a combina-tion of sensitivity and strength : sensitivityto the delicate vibrations which make upthe sound, but strength enough to ensurethat only the right vibrations are heard.

The SME arm achieves this delicatebalance by precision engineering, setting astandard that others have tried to equal.Now with improved lift, the SME armremains the essential component for a

complete sound system.

For complete specifications and inde-pendent reports, write to :

Dept 1039, SME LimitedSteyning, Sussex, England, BN4 3GY

5N]The best pick-up arm in the world

31

Now relax, playfully invite your muse, and transform these tracks,adding body, stereo perspective, flanging, and a host cf other time -base ef-fects. Since Lexicon introduced digital delay over six years ago, most studioshave come to depend on it at least for doubling and slap. Now, the stereo102-S with the new VCO module* produces many other effects, includingmore natural double tracking, flanging, vibrato, time delay panning, extremepitch modulation, and signal transformation for special effects. Of course,you can also use the two channels for completely independent processing.

The Lexicon Delta -T has earned an enviable reputation for its 90dB dynamic range, impeccable audio quality, high reliability, and functionalmodularity. All this is retained in the new 102-S, while two channel operation,finer delay steps (3 ms), and the VCO have been added. And the 102-S iseconomical. Its totally modular construction allows you to start with a barebones mono system and expand later as needs and budget grow. We'll helpyou define the configuration you need to get started. Call or write Lexiconfor further information.

Write on your letterhead for AN -3, StudioApplications of Time Delay.F.W.O. Bauch, Ltd. 49 Theobaki St., Boreham Wood/HertsWD6 4R2, Telephone 01-953 0091.

*The new VCO module also fits any 102-8 or Cmainframe to enhance its time -base signal processing capability.

WalthamMassachusetts 02154 USA

SURVEY: TEST EQUIPMENTSWEEP GENERATORSTV TEST EQUIPMENT

RACALRacal Instruments Ltd, Duke Street, Windsor,Berks SL4 1SB.Phone: Windsor 69811. Telex: 847013.US agent: Racal Communications Inc, 5 ResearchPlace, Rockville, Maryland, 20850, USA.Phone: (301) 948 4420. Telex: 898456.

ProductsFREQUENCY METERSCOUNTER TIMERSDIGITAL MULTIMETERSMODULATION METERSOSCILLOSCOPESRF MILLI VOLTMETERSSIGNAL GENERATORSWATTMETERS

RADFORDRadford Audio Ltd, Ashton Vale Road, BristolBS3 2HZ.Phone: 0272-662301.

ProductsDISTORTION MEASURING SETS*Features: valid readings down to less than 0.002%over audio spectrum. Millivoltmeter available forexternal use. £250, $450.LOW DISTORTION OSCILLATOR*Features: claimed thd less than 0.0020.005% at 10 Hz and 100 kHz.NOISEMETERSVOLTMETERS*See reviews p50

Radford ANM2 Psophorneter

rising to

RANKRank Film Equipment, PO Box 70, Great WestRoad, Brentford, Middlesex.Phone: 01-568 9222. Telex : 24408.

ProductsWOW AND FLUTTER METERFeatures: true rms meter rectifier. Measurementsto CCIR and DIN standards. Max sensitivity 0.1% fsd.

RCARCA Distributor and Special Products Division,Camden, NJ08101, USA.UK: RCA Ltd, Electronic Components, LincolnWay, Windmill Road, Sunbury -on -Thames, Middx.TW16 7HW.Phone: Sunbury -on -Thames 85511. Telex: 24246.

34 10.

ack-of-our"tra

Half the size of Bantam Jacks, the new PCB Jacksare only 1'25" long, 0435" high and 0365" wide.Mount directly on PC Boards wherever access isrequired. Normal through -jack configuration allows

ADC ProductsDIVISION OF MAGNETIC CONTROLS COMPANY

PATENT PENDINT

Following the success of our range of BantameComponents and Jackfields, we have nowintroduced on the U.K. market the first -everJack designed specifically for PCB mounting.

splitting or isolating the signal for test, monitor orpatch.

Available in single or dual configuration.Interfaces with Bantam telephone plugs.

Sic colours available for coding purposes: red, white.blue, orange, yellow and black.For further information on the above, and our rangeof Telephone -type Components, Jack Panels andPrewired Assemblies, contact:

COMMUNICATION ACCESSORIESAND EQUIPMENT LIMITED70-80 Akeman Street, Tring, Herts, HP23 6AJTelephone Tring 1044282) 4011 Telex 82362Ans. Back: Batelcom Tring.

Automatic ResponsePlotting System

By coupling audio analysis plug-in modules toHewlett-Packard's X -Y plotter, Urei offerautomatic frequency response recording, withautomatic rate sensing and control, ensuringaccurate tracing without the necessity of slowsweep rates.

Suitable for hard copy records of tapemachine responses, telephone lines, acoustics,speakers, microphones-Urei Model zoo willresolve to o.o5 dB and has a range up to andbeyond 6o dB. Choice of calibrated sweep andcalibrated frequencies, accuracy is to ± 0.3%full scale. Automatic or manual frequencycontrol, range zoHz to zoKHz.

Full descriptive literature is available on request.

Manufactured byUnited Recording Electronics Industries,11922 Valerio Street, No Hollywood,California, 91605. USA.

0 UNITED RECORDINGU ELECTRONICS INDUSTRIES

F.W.O. Bauch Limited49 Theobald Street, Boreham Wood,Herts. WD6 4RZ Tel: 01-953 oo91 Telex: 27502

33

SURVEY: TEST EQUIPMENT

BROADCAST

PATTERN AUDIO

JACKFIELDS

FROM

FUTURE FILMDEVELOPMENTS

19in Rack Mounting,from one to six rowsof 20, 24 or 26 Jacks.The jacks are moun-ted on a plastic block whichis in turn mounted on a 19inpanel. Each row is fitted witha legend (designation) stripand wire support bar. Thepanel is steel, cadmium plated,chromate passivated and stoveenamelled hammer -tone silver.

ALSO Audio Patch Cords .

Microphone Cable . Installa-tion Cable . Multiway Cable .Post Office and Rendar Jacks. Cable Markers . Lever Keys .Linear Faders . Cannon Con-nectors . Preh Connectors .

Tuchel Connectors . Switch -craft Connectors . Military Tri-Lock Bayonet Connectors .

Audio Attenuators . Wahl andWeller Soldering Irons . PMLMicrophone Accessories .

Hellermann Sleeves and Tools. Crimp Terminals . CableDrums . AB Engineering WireStrippers and DeSolder Guns.

FUTURE FILMDEVELOPMENTS

90 Wardour Street,London W1V 3LETel: 01-437 1892Telex: 21624


ProductsSIGNAL GENERATORSSINE/SQUARE GENERATORS

SOUND TECHNOLOGYSound Technology Inc, 1400 Dell Avenue,Cambell, Ca 95008, USA.Phone: (408) 378 6540.UK agent: C E Hammond & Co Ltd, 105/109 OysterLane, Byfleet, Surrey KT14 7LA.Phone: 093 23-41131. Telex: 262525.

ProductsDISTORTION ANALYSERSFeatures: claimed to measure total harmonic dis-tortion down to levels below 0.002% at settling timesof less than five seconds. Incorporates an oscillatorof 0.001",,, thd.FM ALIGNMENT SOURCESLOW DISTORTION OSCILLATORSFeatures: less than 0.001' residual harmonic dis-tortion over the entire audio band.

SUGDENJ E Sugden & Co Ltd, Carr Street, Cleckheaton,West Yorks BD19 5LA.Phone : 0274-872501.Canada: Reference Audio, 5990 St Hubert, Montreal326PQ.Holland: Audioscript, Nieuw Loosdrechtsedijk 107,Loosdrecht.

ProductsAF OSCILLATORFeatures: RIAA recording curve output. £60.DISTORTION MEASURING SETFeatures: 0.1 full scale deflection, £48.MILLIVOLTMETER

Sugden distortion measuringunit Si 452

WANDEL & GOLTERMANNWandel & Goltermann, Reulingen, Postfach259, West Germany.UK agents: Wandel & Goltermann, 40/48 HighStreet, Acton W3 6LG.

ProductsGROUP DELAYLEVEL METERSNARROW BAND WAVE ANALYSERS

WAVETEKWavetek Inc, 9045 Balboa Avenue, San Diego,Ca 92112, USA.

Phone : (714) 279 2200. Telex : 910 335 2007.UK agent: see Wavetek Indiana.

ProductsFUNCTION GENERATORSGROUP DELAY MEASUREMENTOSCILLATORSPHASE METERSPO LINE TESTING EQUIPMENT

WAVETEK (INDIANA)Wavetek Indiana Inc, 66 North First AvenueBeach Grove, Indiana 46107, USA.Phone: (317) 7833221.UK agents: Wavetek Electronics Ltd, 109 Croc,hamwell Road, Woodley, Reading, Berks.Phone: 0734-694944.

ProductsATTENUATORSSIGNAL GENERATORSSWEEP GENERATORS

WAVETEK SONDMAWavetek Sondma Engineering Division, 161Piner Road, PO Box 1626, Santa Rosa, Ca 9546USA.Phone: (707) 525 8707.

ProductsMICROWAVE COMPONENTSPARAMETRIC AMPLIFIERSUP/DOWN CONVERTERS

WAYNE KERR/FERROGRAPHThe Wayne Kerr Co Ltd, Durban Road, BogusRegis, Sussex P022 9RL.Phone : 02433-25811. Telex : 86120.

ProductsAUDIO TEST SETFeatures: compendium of test equipment compriing low distortion oscillator, millivoltmeter, distortfactor meter, wow and flutter meter and long terspeed stability.LINE TRANSMISSION TEST EQUIPMENTFeatures: for use on PO lines and coaxial rf lineSPECTRUM ANALYSERS

WOELKEWoelke Magnetbandtechnik, 8069 Schweitekirchen, Germany.Phone: 08 444-394. Telex : 55547.US agent: Gotham Export Corporation, 741 Wasington Street, New York, NY10014.Phone: (212) 741 7411. Telex: 129269.UK agent: Lennard Developments Ltd, 206 CheSide, Enfield, Middlesex EN2 OQX.Phone: 01-363 8238.

ProductsDISTORTION TEST SETSFeatures: self -nulling operation-automatic.FLUTTER CLASSIFICATION UNITSWAVE ANALYSERSWOW AND FLUTTER METERS

EMT have an extraordinarily versatile flutter meter at aprice you can afford-the new low cost EMT 422.

Flutter and FIM (frequency inter -modulation) distortionmeasurement can be made in five ranges from 0.1%to o()/0 FSD to DIN/ANS I/IEC standards. In addition,three further filters can be selected for a rapid initialanalysis of flutter frequencies. Weighted peak and slowspeed deviation values are clearly displayed on separatelarge size meters.

A unique feature is the programmable thresholdlevel option which provides an instant visualindication at three preset levels for simplifiedquality control and production line testing.

Outputs are provided for use with externalfilters, graphic recorders or oscilloscopes tofurther extend the EMT 422's unique capabilities.

Manufactured byB.M.T.-Franz Vgmbh,P.O. Box 1520, D-7630. LA HR1West Germany.

For the Flutteryo

afford

F.W.O. Bauch Limited49 Theobald Street, Boreham WoodHerts. WD6 4RZ Tel: or -953 0092 Telex: 27502

109 PROL1NE PROFESSIONAL

SOUND

SENSE

IN

'77"O.

Excellent performance, ruggedly reliable and economicallypriced, what could be more sensible these days. A demonstrationis just a phone call away. Contact the United Kingdom's largestand most experienced manufacturers of professional recorders.

LEEVERS-RICH Equipment Limited,(Incorporating Bias Electronics)

319 Trinity Road, London SWI8 3SL. 01-874 9054Cable: Leemag London SWI8

Telex: 923455

A Mini Mixer with a truePROFESSIONAL STUDIO SPECIFICATION

11111111.11. alla Ili aa 6. 4, 4Y elf A& 4ff

AM lifa

14/4 Custom Console basedon Mini Mixer modules.

STANDARD MIXER10 Input Channels, 4 Output Groups.Auxiliary Sends and Echo Returns.

XLR Connectors to balanced Mic Inputs and Line Returns.Normalled Insert Jacks.

Low Noise and High Output levels.Portable.

Extension units, PPM's, Limiters etc. also available.SOUTH AFRICA BELGIUMProsound, Musicians Sound ARC, SPRL, BrusselsCentre, J'burg. Tel. 642-87-21 Tel. 771-30-63SPAIN DENMARKTELCO Sociedad Limitada Audiophil, Copenhagen FMadrid. Tel. 221-5606 Tel. (01)fa. 5209HOLLAND WEST GERMANYPieter Bollen, Eindhoven Elmus GmbH, Berlin 12Tel. 040-512777 Tel. 030-312-2012

RAINDIRK LTD., Downham Market, Norfolk.Tel. 2165 and 3617

35

Tape machine maintenance

DAVE DEARDEN

Maintenance engineers probably clockup more overtime while servicing tapemachines than with any other piece of studioequipment. Replacement of folklore byscience cuts bills and, in the end, makeslife much easier for all concerned.

*Mt (UK) LTD

POSSIBLY the most misunderstood, and usually the mostmaladjusted piece of equipment in a recording studio, is the

tape recorder. Because it is a combination of sophisticatedelectronics and mechanics, confusion sometimes exists as to thecause of its ailment when it malfunctions. A mechanical fault canoften give electronic like symptoms, and vice versa. Also, a badlyslit tape will often appear to indicate that the mechanicalalignment of guides and heads is in need of adjustment. Unevenoxide coating of the tape can give bizarre modulation effects. Acareful and logical approach is necessary in order to achieveoptimum performance from a machine, coupled with anunderstanding of the basic techniques involved.

It is hoped that the following will impart some of the techniquesand provide a greater understanding of the mechanical andelectronic adjustments which are made.

Mechanical alignmentTape heads require four accurate adjustments if the machine is toperform to specification.Height. To set the track pole -pieces to the correct position on thetape.Zenith. To set the head face perpendicular to the deck, ie parallelto the tape.Wrap. To set the headgap at 900 to the tape, viewed from above.Azimuth. To set the headgaps at 90° to the tape, viewed from thefront.

Height can normally be set by visually aligning the head forequidistant spacing between the top and bottom shield plates andthe edges of the tape. If the shield plates are not visible, transparentleader tape can be used and the track pole -pieces viewed.

For the adjustment of DIN stereo heads, where the track spacingis much closer than multitrack heads, a test tape is available with


signal recorded along the centre of the tape, ie in the guard -band.The head height is then adjusted for minimum signal from bothtracks.

Zenith is an important and often neglected adjustment whichgives equal head to tape contact across the width of the tape.This ensures even head wear across the head, and is essential inmultitrack machines for good tape tracking, as the tape will tendto slide upwards or downwards across a non -vertical surface.Maladjustment is easily recognisable after the damage has beendone, as the wear -pattern across the head will have non -paralleledges. Unfortunately, when it has reached this state, the cure iseither relapping the head or replacement. Realignment of anasymmetrically worn head usually results in bad head contactacross part of the head stack, and tape mistracking on multitrackmachines. The moral of the story is to align it correctly in the firstplace.

The usual method is to smear a thin coat of ink across the headface, put the machine in the play mode for a few minutes and thenobserve the wear -pattern, adjusting until a parallel wear -pattern isobtained. Another method involves the use of a set -square to setthe angle from the deck to the head face at 90°. On certain machines,this method is not possible, either because of obstruction in frontof the heads, or because of deck trim plates which are not

°FIG.I RESPONSE OF38 cm/s DIN TESTTAPE REPRODUCEDWITH NAB 0

EQUALISATION

.5

20 100

FREQUENCY IN Hzto K 20K

necessarily in the correct plane.The quickest, simplest and most accurate method so far used is

an aluminium block, precision ground, about 10 x 4 cm. This isbridged across from a known vertical surface to the next surfacealong the tape path. By holding the block against the face of theknown vertical, usually a fixed guide, and gently pressing theopposite end against the next surface face, extremely small amountsof non -parallelism can be felt as the block will rock to and fro ifthe two surfaces are not parallel. Proceed through the tape pathuntil all heads, guides, and the capstan, are vertical.

Wrap is another neglected adjustment, which will affect thehigh frequency response. This is easily checked by playing the16 kHz band on the test tape, and slightly increasing the backtension by lightly touching the supply spool. If the signal levelincreases then the wrap adjustment is incorrect. Adjust the headwrap for maximum signal at 16 kHz, and minimum change whentouching the supply spool. It should be possible to achieve lessthan 0.25 dB change. The check should be repeated for the recordhead, in the sync mode, or if the machine does not have a syncmode, by recording 16 kHz and observing the playback level.The erase head is much less critical, but can be adjusted formaximum depth of erasure.

Azimuth adjustment is normally achieved by playing the azimusection of the test tape, combining all tracks at similar levels, andadjusting for maximum output as viewed on a meter. Ensure thatthe real maximum is found, as there will be lower level peaks oneither side of the real maximum. This method gives an averagevalue azimuth adjustment across the whole head stack.

FIG.2 RESPONSEOF19cm/s DIN TEST °TAPE REPRODUCEDWITH NAB dB

EQUALISATION5

20 100 1K

FREQUENCY IN Hz

100 20K

Another method utilises an oscilloscope to display Lissajouspatterns from two widely spaced tracks of the test tape, excluding theedge tracks. This is to minimise disturbance of the pattern due todropouts. This method gives minimum phase error between twotracks, but could be in error between other tracks, due to gapscatter and inaccuracies in the manufacture of the head stack. Tocheck this, use one track as a reference and check all other tracksagainst it.

A simpler method than the above is to display the two trackson a dual beam scope and adjust for minimum phase errorbetween the two signals. Ensure that the scope is set to theswitched or chopped trace mode, not the alternate mode, which willnot display phase related signals correctly.

Because of the short wavelength of high frequency signals, it ispossible for the signal to appear correctly in phase while in factbeing one or more complete cycles displaced. This would meanthat signals at other frequencies would be in error. To guardagainst this, always start at a low frequency and make gentlecorrections as the frequency increases, always keeping the twosignals in phase. Short term phase jitter up to about ±90° will beobserved at the higher frequencies and azimuth should be adjustedto give equal positive and negative displacement. If larger amountsoccur, it implies either a damaged test tape or mechanicalmaladjustment of guides and rollers. The latter would cause theformer, of course, and should be corrected before a new tape isused on the machine.

The same method is used to align the record head when a syncmode is available. On machines without sync, record head azimuthis adjusted by recording and simultaneously observing the playbacksignal. The erase head azimuth is not normally critical, but can beadjusted for maximum depth of erasure.

A point which must be borne in mind, with certain headmounting arrangements, is that some of the mechanical adjustmentsare interactive to a degree; for instance, head height will usuallyaffect the other parameters, which must then be re -adjusted.

Electrical adjustment-playbackPlayback Level. The required playback level is set by using the`Reference Level' of a test tape. Unfortunately, a number ofdifferent reference levels are used by different manufacturers, soleading to confusion unless the relationship between the variouslevels is understood. See 'Reference Levels' by Hugh Ford-STUDIO SOUND (January 1977, p 42).

Fluxivity nWb/m

185 nWbim200250320

Flux level (dB)ref 200 nWb/m-0.7

0

-1-4

Ampex operating levelMRL reference levelMRL elevated levelDIN reference level

The required playback level is determined in conjunction with thetype of recording tape to be used, and also the line level used inthe studio. Normally the majority of studios operate at a line levelof +4 dBm. The standard vu meter will read 0 vu with a +4 dBmsignal applied to it.

So, if it is required to operate at 'elevated level', all that is

necessary is to adjust the tape recorder playback level to give0 vu when playing a 250 nWb/m test tape. If a test tape witha different flux level is available, then the playback level is adjustedto compensate for the difference in flux levels, for example, a200 nWb/m test tape would read -2 vu if 0 vu were required toindicate 250 nWb/m. The difference between any two flux levelscan easily be calculated by the formula:Difference (dB) = 20 log Flux 1

Flux 2Frequency Response. The playback response is set by using thefrequency response section of the test tape and adjusting the highand low frequency controls of the lest tape for flattest responses.Test tapes with NAB equalisation usually have the response sectionrecorded at the same level as the reference level. This allowsresponse adjustments to be made using the tape machine meters.On the other hand, DIN equalisation test tapes usually have theresponse section recorded at -10 dB or -20 dB relative to thereference level, necessitating the use of an external ac millivolt -meter to indicate levels. When aligning a multitrack machine, thismeans a considerable amount of time being wasted in pluggingthe meter from track to track. An NAB machine can usually bealigned solely on its internal meters, allowing all tracks to be seenat the same time.

When adjusting the low frequency responses, allowance has to bemade for the effect of 'fringing'. This is due to the test tapebeing recorded as a full track tape, instead of individual tracksacross the tape. Due to the long wavelengths at low frequencies,the head picks up a certain amount of spill from either side of thetrack width proper. This adds to the overall signal level, ie it givesan apparent increase in flux level at low frequencies. If this levelis used without due allowance, the low frequency response of thetape machine will end up deficient by the amount of fringingaddition when playing a normal recorded track width equivalentto the playback track width. The amount will vary from one headmanufacturer to another, and is related to the efficiency of the lowfrequency shielding built into the head. Certain test tapes havecompensation incorporated, and care must be taken in knowingwhether or not a compensated tape is being used. If anuncompensated tape is used, the low frequency response shouldbe allowed to show a rise of approximately 3 dB at 50 Hz. A moreaccurate and consistent method is to leave the low frequencyadjustment until the record alignment is performed. Then, byrecording at frequencies between 40 Hz and 150 Hz, the flattestoverall response may be obtained. It will be noticed that theresponse will not be flat, but will show a series of bumps andtroughs. This is caused by the shape of the head pole pieces and isalso influenced by tape speed.

Occasionally, it is necessary to align a machine to one equalisationstandard using a test tape of a different standard. This is simple ifconversion tables are available. The most common conversionsare DIN 38 cm/s to NAB 38 cm/s, and DIN 19 cm/s to NAB19 cm/s, and vice versa.

Record alignmentBias. Bias setting can be performed in a number of ways. Themost common method is to record a 1 kHz signal, and whileincreasing the amount of bias observe the playback -level until afurther increase in bias causes the playback level to decrease. At thispoint continue increasing the bias until the playback level hasdecreased by approximately 1 dB. The amount of overbias willvary from tape to tape, and should ideally be found by measuringthe distortion produced by the tape at different bias levels. Thepoint of minimum distortion is usually taken as the correct biaspoint. If the decrease in the level from peak bias is now noted,this overbias point can be used to bias all other tracks, withoutthe need for the distortion analyser. It is usually more consistentto over bias at 10 kHz, where the amount of level decrease willnormally be about 3 dB. This is easier to see, and results in moreaccurate biasing.

Another method is to bias for minimum modulation noise, byrecording a very low frequency such as 3 Hz. The bias is thenadjusted for minimum noise. However, on most modern tapes, theminimum distortion point and the maximum modulation noisepoint are usually very close together, and it becomes a matter of

38

37

fItteisDear Sir, Congratulations on an excellentAugust 1976 issue. It contains many extremelyinteresting features and the 'inside information'on Abbey Road is certainly deserving of thelarger exposure that you have now given it.

Perhaps it is not surprising that such aninteresting issue should evoke some commentsof a more or less serious nature.

The first is not so much a complaint as aserious epidemic, and it is reassuring to learnthat Drs. Blair, Peckham, Davies and theirprofessional colleagues have the antidote(literally) at their fingertips. I refer to thecurrent resurgence of the frenetic struggle formore and more level on disc records. For thosewho may not be aware of the magnitude of theproblem I would point out that recorded veloci-ties greater than 50 cm/s at 10 Hz are now byno means uncommon.

Being deeply involved in the design of recordplaying equipment for domestic use, I wouldlike to suggest that what the cutting fraternityare trying to do is actually self-defeating. Thestate of the art in low -price record players atthe beginning of 1976 was that adequate overallgain and signal-to-noise ratio, together withadequate bass response, could be obtained byusing a crystal pickup cartridge and a simplediscrete or integrated amplifier. This could givevery acceptable results for an outlay of between£40 and £50. (Just to quantify, 'adequate' gainmeans that the amplifier is driven tomaximum by a recorded velocity of 3 cm/s at4 kHz with the volume control at maximum;`adequate' s/n is -60 dB ref. max. output CCIRweighted, and 'adequate' bass response is -3 dBat 50 to 70 Hz, with or without peaking.) Earlylast year the industry began to receive manycomplaints of pickup jumping and generaltracking failure on products which up to thenhad been perfectly complaint -free. It was fairlysoon clear that some labels were particularly

testing, notably B*££. The only practicalsolution was to abandon the crystal cartridgeand use a ceramic, with improved trackingcapability but with 3 to 4 dB less output! Thegain loss had nullified the increased level onthe disc, and the amplifier (believe me) cannotbe modified to give more gain without com-promising the cost (not recoverable due to thePrice Code!), the s/n or the bass responseunacceptably. Nett result-sorrow all round.Perhaps the 'friendly rivalry' and jolly japeswill be tempered with a little thought along theabove lines in future! One wonders whetherMr Blair has 'slapped in a V15/III' on his cheapgramophone (sic).Yours faithfully, J. M. Woodgate.

P.S. Very high recorded velocities cause un-necessary problems in higher quality equipmentas well. In spite of the fact that many existingdesigns are less than adequate in this respect, itis not difficult to design a magnetic pickup(RIAA) equaliser to accept 50 mV input or evenmore. However, it is quite difficult to obtain avery good noise performance simultaneously,and the noise, like the poor, is always with us.Thus, either the equipment cost is increased orthe increased recorded level results in anunchanged, or even reduced, dynamic range.J.M.W.

Ken Townsend replies:We sympathise with the problems mentioned

by J. M. Woodgate, but an instant remedy isnot possible. Record producers naturally insistthat their records are cut at the highest levelpossible to compete with the opposition. Ifone cutting room will not oblige then they willtake their work to one that will. For our own

part, we at Abbey Road realise that recordshave to be played on not only good equipmentbut also on the very cheapest. We have astandard low quality, low price, record player'which is used to check that pop records do notjump, and any which fail the test are re -cut.We therefore earnestly try to satisfy not onlythe needs of the record producer but also therecord -buying public at large.

Mr Woodgate admits in his letter that he ishaving to keep the price at a minimum in orderto compete with other low-priced players, andif all' such manufacturers designed to a slightlybetter standard then the problem would bealmost eliminated. We have actually purchasedfrom customers who have complained about'umpers' their disc -playing equipment, in orderto assess the industry minimum standard, notonly in London but also in Europe and theUnited States.

Dear Sir, We have recently been expanding ourstudio facility and have purchased quite a fewitems of professional recording equipment fromthe country's major suppliers.

We wish to take this opportunity of expressingour appreciation to the following companies fortheir swift, efficient and polite service, as every-thing we ordered arrived within two weeks ofordering, and this saved us valuable down time.

B&K LABS,DOLBY LABS,AUDIO AND DESIGN RECORDING,SCENIC SOUNDS,ITA,ALLEN & HEATH,TANNOY,KLARK TEKNIK,H/H ELECTRONICSURREY ELECTRONICS,FWO BAUCH.We hope that future transactions can be done

as swiftly with other companies.Yours faithfully, P. G. Adshead, Pennine SoundStudio, Gladstone Street, Oldham, Lancs.

TAPE MACHINE MAINTENANCE

personal preference which method is used. Ideally, bias should beset independently for each speed, but certain machines do not havethis facility. In this case, bias should be set for the most used speed.If the 10 kHz method is used, on DIN machines, the record levelshould be about -6 vu to avoid possible high frequency compression,which could give erroneous results.

Record Level. Once the bias has been set, the record level canbe set. This is dependent on the type of tape to be used. Thenewer tapes allow a greater record level, without increasing thedistortion produced, thereby giving a greater signal-to-noise ratio.The majority of studios appear to be recording at elevated level,ie 0 vu equals 250 nWb/m, although some are recording 2-3 dBhigher using tapes such as Scotch 250 and Ampex Grand Master.This is especially common in studios running at 76 cm/s without38 STUDIO SOUND, FEBRUARY 1977

noise reduction systems, and in general, excellent results arereported.

Record Equalisation. Record frequency response is set byrecording various frequencies between 40 Hz and 16 kHz and settingthe high frequency equalisers for flattest response. As mentionedearlier, the low frequency signals are used to set the playback lowfrequency equalisation. Again, on DIN machines, the maximumsinewave alignment level should be reduced to avoid tape compression.

The foregoing is by no means intended to be a complete guide totape machine alignment, but to provide a degree of illuminationto the unwary of the pitfalls involved in routine alignment, and togive some idea of the various methods commonly used to achievealignment. Other methods exist, but usually require the use of testequipment not normally found in the average studio, and soemphasis has been placed on methods of alignment using theminimum amount of external equipment.

*0000000 0000000000 00 000000000 00

SALES and:SERVICE :Telephone: Cardington 404 Specialists in Service and Repair of T.R.D. recorders. All parts, motors, etc., available. Collection and delivery: London and Home Counties.

FOR SALESends 0

Helios 20-16-16

00

0

0£325

TRAD

Sound Techniques System 12, 18-4-16API 24-8-16 12 months old...3M M56 16 track ...

6 Ampex 1100 24 track, fromI Ampex MM 1200 24 track3 MM 1100 16 track, from ...

2 Studer A62's on trolleys with V.U.Leevers-Rich 8 trackTeac 3340 'S', as newAll A.K.G. mics in stock, new and secondhand.Selection of Beyer mics in stock.

I Pair Lockwood Majors with Tannoy RedsJ.B.L. 4502 Studio Monitors, immaculate

condition, per pairI Pair Spendor BC3'sBrand new Microphone Boom Stands

with Mic. Clip, each ... f 15

2 Dolby A301 units, each ... £300I Dolby MI6 unit ... £3,500Urie Graphic Equaliser 27 frequency ... £320

Zonal Tape, lin, lin, 2in.

Neve 24-8 Desk, 4 Compressors, 8 Echo... £9,500

L9 750

Spectrasonics 24-8-24 eight months old ... £16,500Audio Developments 16-4 £1,500

Audio Developments 20-20 with 16 trackmonitor desk ... £4,500

Sound Techniques 24-8, nice condition £3,750

... £5,000

... £16,500

... £7,500

16,000

19,250

... £9,000

I ,I00... £3,800... £550

WANTED - ALL STUDIO EQUIPMENT

Desperate for A80 16 -track.

DOG HOUSE,BEDFORD ROAD, COPLE,

BEDFORDSHIRE MK44 3TRTelephone: Cardington 404

£320

£650

PORTABLE

21104 -VAT.

AC V, I & dB:

DC V, I & NULL:

RESISTANCE:

LEAKAGE ar 3V:

V DROP at 10mA:

HIGH VOLTS:

RF VOLTS:

TEMPERATURE:

HIGH CURRENT:

120 BASIC RANGES5011V/500V fsd, 50pA/500mA fsd, -90dB/±50dBmid scale. Acc. +1.5% fsd ab ove .5001.1V & 500pA.Response 3Hz/200kHz above 500µV and 500nA.Input R=100MS.1 on volts.150uV/500V fsd, 150pA/500mA fsd, polarityreversible. Acc. ±I.5% fsd above 5001.1V & 500pA.Input R= 100M0 on volts. 5 Null ranges havecentre zero lin/log scale covering ±4 decades.0.252/10GSI in 7 ranges, polarity reversible.Low test voltage for solid state circuits.Uses 3V source with current ranges to testcapacitors, diodes and resistance up to I OOG Q.Uses 10mA source with voltage ranges to testdiodes, LED's and resistance down to 10m0.

30 OPTIONAL RANGES1.5kV/50kV fsd, AC/DC, using HV Probe type TPI,£16 plus VAT.0.5V/500V fsd, 10kHz/IGHz, using RF Probetype TP2, £22 plus VAT.-150°C/+500°C fsd in 7 ranges using TemperatureProbe type TP4, £38 plus VAT.1.5A/50A fsd, AC/DC, using Current Shunt type TP5,£15 plus VAT.

The instrument operates from a 9 volt battery, life 1000 hrs., or ACmains when an optional Power Supply Unit is fitted.Size is 240mm x 150mm x 80mm. Weight is I.75kg. Meter scale lengthis 140mm. Leather case type LC7, £13 plus VAT is an optional extra.

LEVELL ELECTRONICSLIMITED

MOXON STREET, BARNET, HERTS., ENGLAND, EN5 5SD.TEL: 0 I -449 5028/440 8686

39

Survey test discs and test tapes

Most test softwaremanufacturers will provideproducts to a wide variety ofspeeds and standards. IndividualA--mnbinations should be checkedd;rectly with the supplierbefore ordering.

PART ONE: Test Discs

B & KBruel & Kjaer, 23 Linde alle, DK-2850, Denmark.Phone : 01-80 05 00.US: B & K Instruments Inc, 5111 West 164th Street,Cleveland, Ohio 44142.Phone: (216) 267 4800.UK: B & K Ltd, Cross Lances Road, Hounslow,Middlesex. Phone: 01-570 7774.Q R2009Stereophonic gliding frequency recording.QR2010Comprehensive laboratory disc.QR2011Testing and adjustment of hi-fi systems with1 -octave pink noise.

CBSCBS Technology Center, 227 High Ridge Road,Stamford, Conn 06905, USA.Phone: (203) 327 2000.UK: Feldon Audio Ltd, 126 Great Portland Street,London W1. Phone: 01-580 4314.STR 151Broadcast test record to RIAA standard.STR 100Stereo frequency test record.STR 101Seven steps to better listening; lining up record fordomestic equipment.STR 112Squarewave, tracking and intermodulation testrecord.STR 120Extended frequency test record; 10 to 500 Hz, 500 to50k Hz glide tones.STR 130RIAA frequency response test record for calibra-tion of professional replay equipment.STR 140Pink noise tests for acoustical testing of systemsand loudspeakers and for psychoacoustic tests ofreproduction equipment.STR 170This record employs a 318 us equalisation charac-


teristic with constant amplitude recording below500 Hz and constant velocity above this point.SQT 1100Quadraphonic test record for calibration, verificationand adjustment of SQ replay systems.

DECCADecca Records Ltd, 9 Albert Embankment,London SW1. Phone: 01-735 8111.SXL 2057Stereophonic frequency response test disc with spotfrequencies.

DGGBeuth-Vertreib GmbH,1000 Berlin 30,Burggrafen-strasse 7, Germany. Also 5000 Koln, Friesenplatz16, Germany.UK: Lennard Developments Ltd, 206 Chase Side,Enfield, Middlesex EN2 OQX. Phone: 01-363 8238/9.Deutsche Grammophon Gesellschaft manufacture afamily of test discs to calibrate replay equipment to thefollowing DIN standards:45 541 frequency response45 542 distortion45 543 crosstalk45 544 rumble45 545 wow and flutterThe company also manufactures a range of discsintended for other measurement purposes:1001 94217 cm disc with 5 kHz carrier for wow and fluttermeasurement to DIN 45 507.1001 94417 cm disc with 3 kHz carrier for use with wow andflutter meters such as the EMT 418.1101 49517 cm disc for testing stereo replay equipment; itgives channel and symmetry information, loud-speaker phasing etc. The flip side is an assortmentof everyday noises. This disc is available withannouncements in French or English.1099 008, 1099 01030 cm versions of 1001 942 and 1001 944 respectively.1099 01130 cm disc with 45 rpm playing speed for measuringintermodulation distortion to DIN 45 403 sheet 4.400 Hz + 4 kHz in the absolute velocity ratio of 4:1.1099 01430 cm disc for demonstrating the audibility of band-width distortion.1099 01530 cm disc for demonstrating the audibility of nonlinear distortion.1099 103Level measurement at 45 and 33 rpm.1099 106Frequency response measurement to DIN 45 547.1099 108For testing intermodulation distortion of pickups byuse of a gliding pair of tones with 400 Hz difference.1099 109Warble tone for loudspeaker tests.1099 111Tracking tests.1099 112Universal frequency measurement disc containingglide tones and spot frequencies.1641 001Hi-fi stereo test disc.

EMIEMI Records Ltd, Manchester Square, LondonW1. Phone: 01-486 4488.TCS 101A stereo frequency response disc with a recorded

equalisation characteristic to British Standard1928!1960, except that the level of frequency bandsabove 10 kHz has been dropped by 6 dB. Spot ire-. quencies and reference tones.TCS 102A series of glide tones for detecting resonances.TCS 104As TCS 101 but in mono only (lateral modulation).TCS 105As TCS 104 but with vertical modulation.TS 201 and TS 202Tracking ability to British Standard 4852: Part 1, 1972.RLPS 22Wow and flutter.

HI-FI NEWSLink House Publications, Link House, DingwallAvenue, Croydon CR9 2TA.Phone: 01-686 2599.QUADRAFILEA two record set featuring the four major quadraphonic systems on successive sides; the same poshtional tones and musical material is recorded in SQ,QS, CD -4 and UD-4 for comparison purposes.

HI-FI SOUNDHaymarket Publishing Group, Gillow House,!Winsley Street. London W1. Phone: 01-4394241HFS 75This test record is intended for both aural anquantative testing of turntables and cartridges.

JVCJVC Cutting Center Inc, RCA Bldg, Suite 5116363 Sunset Boulevard, Hollywood, Californi90028, USA.UK: JVC (UK) Ltd, Eldonwall Trading EstaiStaples Corner. 6-8 Priestly Way, London NW27APhone: 01-450 2621.TRS 1001Mono disc for checking frequency respellmechanical resonances, etc.TRS 1002Stereo disc for checking frequency response, arand flutter, etc.TRS 1003Stereo frequency response record for testinghigh frequency response of CD -4 pickup cartridpTRS 1004A record cut for undertaking quick checks of 11frequency response, crosstalk, and phase of CIcartridges. Primarily intended for checks durproduction.TRS 1005Record for high frequency response and MSS'checks on CD -4 cartridges using level recordsuch as the B & K 2305/2307.TRS 1300High frequency response and crosstalk.

SHUREShure Bros Inc, 222 Hartrey Avenue, Evans'III 60204, USA.UK: Shure Electronics Ltd, Eccleston Road, hlstone ME15 6AU. Phone: 0622-59881.TTR 110'An Audio Obstacle Course'. All sorts of nalwhich highlight deficiencies in cartridges.TTR 102Tests low frequency resonance and intermodulidistortion.TTR 103Disc intended for disc tracking tests-for useexternal analysis equipment.TTR 109Level and crosstalk record for use with enanalysers.

MRL Test Tapes offer improved performance-and save you time and money because-

You will have confidence in theiraccuracy. Each MRL tape isindividually calibrated duringmanufacture and accompanied by testresults and certification.MRL alignment tapes contain thesignals and levels required for testand calibration of your reproducingsystem.Less time is needed for reproducertest and adjustment because of themore comprehensive and convenientMRL formats.Your specific reproducing systemparameters and signal chaincharacteristics are readily measuredwith specialised MRL test tapes andcompanion reference products.Manufactured byMagnetic Reference Laboratory Inc.,229 Polaris Avenue, Suite 4, Mountain View,California, 94043, USA.

PART TWO: Test Tapes

AGFAAgfa-Gevaert AG, Vertrieb Magnetband, D-509Leverkusen, West Germany.US: Agfa-Gevaert Inc, 275 North Street, Peter-borough, NJ 07608.Phone: (201) 288 4100.UK: Agfa-Gevaert Ltd, 27 Great West Road, Brent -ford, Middlesex TW8 9AX.Phone: 01-560 2131.

The company manufactures a range of recording testtapes in a variety of widths and speeds to the DIN/IEC format only. No further information received.

AMPEXAmpex Corporation, Audio -Video SystemsDivision, 401 Broadway, Redwood City, Ca94063, USA.UK: Ampex Great Britain Ltd, Acre Road, Reading,Berks RG2 OQR.Phone: 0734-85200.

The company manufactures a range of test tapes inall size formats between 6.25 and 50 mm; these areavailable both in full and separate tracking. Speedstandards are 76, 38, 19 and 9.5 cm/s (the last speedis available only in 6.25 mm size).

Equalisation standards are to either DIN or IEC(76 cm/s uses 17.5 ps AES).

Tapes are available in three groups: reproducealignment tapes, flutter test tapes and level set tapes.

The first group offers operating level tones at 11spot frequencies at operating level (38 and 76 cm/sonly). The lower speed tapes use -10 dB tones atappropriately reduced frequencies. They also incor-porate extended azimuth and 700 Hz reference tonesrecorded at operating level (lower speeds -10 dB).

Flutter tapes use tones of either 3000 or 3150 Hzrecorded at -2 dB below operating level. These areguaranteed to have less than 0.03% rms unweightedwow and flutter.

Level set tapes comprise long sections of 700 Hzat various standard flux levels resulting in approxi-mately 1% total harmonic distortion.

BASFBASF AG, 67 Ludwigshafen -am -Rhein, WestGermany.Phone : 621 40081.US: BASF Systems Inc, Crosly Drive, Bedford,Mass 01730.Phone: (617) 271 4000.UK: BASF United Kingdom Ltd, KnightsbridgeHouse, 197 Knightsbridge, London SW7 1SA.Phone: 01-584 5080.

The company manufactures a range of test tapes inall size formats to the IEC/DIN specification only. Nofurther information received.

EMIEMI Sound and Vision Ltd, 254 Blyth Road,Hayes, Middlesex U B3 1HW.Phone: 01-5733888.

SRT 17 and 18Tape speed 38 cm/s and 19 cm/s respectively.Equalisation 35 As and 70 us DIN. Wow and fluttersection with recorded 3 kHz tone at less than 0.08%rms unweighted.

A speed check of stroboscopic markings on tapebacking for view with a mains 50 Hz neon lamp.

A 1 kHz tone recorded at a flux of 320 nWb/mlasting for 20s.

An azimuth adjustment tone of 16 kHz lasting for40s.

A series of frequency response tones each of tenseconds duration preceded by an announcement.SRT 19This tape offers the same tests as the SRT 17/18 butat a tape speed of 9.5 cm/s. Some tests have beenmodified to accommodate this speed.

The SRT 18 test tape is available in cartridgeformat designated SRT 18C. All the above are 6.25 mmwide.

MRLMagnetic Reference Laboratory Inc, 229 PolarisAvenue, Suite 4, Mountain View, Ca 94043, USA.Phone: (415) 965 8187.Export agent: Gotham Export Corporation, 741Washington Street, New York, NY 10014, USA.UK: FWO Bauch Ltd, 49 Theobald Street, Boreham-wood, Herts.Phone: 01-953 0091.

Standard equalisation tapesStandard MRL test tapes have a reference fluxivity of200 nWb/m which is appropriate to tapes such as thegeneration prior to the 3M 206 etc. The company alsomanufactures a range of test tapes corresponding toa maximum flux of 250 nWb/m for the so called 'highoutput' tapes.

Product line includes tapes which incorporaterapid sweep (for technical reasons, these arerestricted to frequencies above 500 Hz; checksbelow this require standard tones at spot frequen-cies). There are also a range of tapes with the usualspot frequencies throughout the audio spectrum.Tape width 6.25, 12.5, 25 and 50 mm. Normal eqstandard; NAB 50 + 3180 us. Tape speed 19, 38 and76 cm/s. IEC equalisation test tapes are available inthe above tape width sizes referenced to a fluxivity of320 nWb/m.

MRL also produces a range of azimuth correctiontapes using an alternate tone difference measure-ment process for correct adjustment.

Calibrate in Confidencewith MRL Test Tapes

MRLMAGNETIC REFERENCE LABORATORY

F.W.O. Bauch Limited49 Theobald Street, Boreham WoodHerts. WD6 4RZ Tel: 01-953 0092 Telex: 275o2

41

icroek

Well respected KonkIt used to be the done thing for anemergent Rock Star to lavish hisnew-found riches on a limousinefor himself, a country seat for hismuch -loved parents, and maybe, acouple of record shops. Well timeschange as, thankfully, does themusic industry-and the currentsuperstar status symbol seems tobe the possession of one's ownstudio. Among the first groups torecognise the inherent economicsense of this were the Kinks, whosecareer had successfully spannednearly a decade when they decidedto buy their own studio in 1971.They called it Konk, and some fiveyears later, the name is about theonly thing that's remainedunchanged.

Konk started out life as a

Victorian tobacco warehouse,although by the time it was con-verted into a studio, it had degener-ated into a motley and ratherdilapidated collection of garages.The original idea was that itshould mainly be used for demowork by the Kinks, but an 8 trackwas installed from the start toleave room for expansion. After acouple of years, increasingly com-plex recording commitments led tothe acquisition of a 16 track system,which led to the studio getting a lotmore outside work. This trendwas continued when, earlier thisyear, the studio was completelyrebuilt and re -equipped, to emergeas a fully commercial 24 trackoperation.

Not for Konk, the bright lightsand astronomical overheads of theWest End. Instead, the studiolives in the less salubrious end ofHornsey. What it loses on location,it doesn't lose on accessibilitythough. It's within easy reach ofthe North Circular and M1, andthe average Roadie should be ableto dice his way from Konk toLondon Airport in under an hour.

From the outside, the only thingwhich distinguishes it from a streetof prim, slightly decaying semis isthe de rigeur smoked glass land-scape window that hides the recep-tion area from the gaze of thecurious. On the day we turned up,the heavy oak door was opened bynone other than Ray Davis, a heroof our photographer's mis-spentyouth. He doesn't usually act as


doorman though, he just happenedto be nearer than anyone else. Itturned out in fact that the Kinkswere in the studio recording theirnext album, but a bad case ofmonitor dropout had called a haltto the proceedings, while the manfrom Neve groped around the darkand intricate recesses of the boardto try and find the cause.

To get from the reception areato the studio you go through averitable labyrinth of narrow corri-dors and light, airy practice rooms;and the feeling is of somethingbetween an old fashioned musicacademy and rambling countryhouse. Go through the heavydouble doors and into the studioproper, and it's another story. Thenew Konk, you see, was not just asimple refurbishing job on theexisting building. Instead, a separ-ate self-contained shell has beenbuilt up inside the structure of theold warehouse, and resting on anextremely solid poured concretefoundation.

The control room is impressivelylarge-it will seat up to 19 peoplewith ease-fully air-conditionedand subtly lit from overhead lighttracks. Its layout and equipmentreflect the ideas and experience ofone man, Roger Wake; StudioManager, Recording Engineer andgeneral factotum at Konk. Whenhe came to Konk, he inherited theold 16 track setup, so the changeto 24 gave him the chance to set

things up exactly as he wantedthem. After nearly 10 years in thebusiness, including a long spell atPhonogram and a period as anindependent radio commercial pro-ducer, he had a fairly good idea ofwhat he was after and, generallyspeaking, feels that he's got it withthe new studio.

You can't have things 100 percent perfect though, and in Roger'scase this meant that he had to forgothe pleasures of a custom-built Nevedesk, because he'd have had a waitof over a year for delivery. Thiswould have gone way over theschedule for converting to 24 track,so he settled for a standard framewhich has been considerably re-worked, but only took six monthsto build and install. The modifica-tions are, says Roger, designed tomake the board more ergonomicin use, and they include a central-ised monitoring panel which wastaken from another frame, andsliding faders instead of the stan-dard stub rotaries. Also, the stan-dard Neve limiters have beenreplaced by Audio & Design units.

A Sony cassette recorder is per-manently mounted on the board.This can be used to take instantrun-offs of finished masters orindividual takes. There are 24input channels-although the boardis wired for 32 and the others mightbe hooked up soon-and 24 out.The channel amplifiers are Neve'smost sophisticated, with 20 pres-ence frequencies. EMT stereoplates, and four separate echo sends,each with individual level controls,are used. Likewise, there are fourseparate foldbacks, each of whichcan be independently balanced.

One of Roger's hangups fromhis Phonogram days was the rela-tively low playback level of theresident Tannoy monitors: 'Iremember a couple of Status Quosessions where the group were play-

ing very loud and we just couldnget enough sheer volume on pla!back through the Tannoys treproduce the original levels acctrately. I've obviously got a lotrespect for them, and I like usinthem-but they're really just rubig enough for modern rocrecording.' To make sure thrKonk doesn't have similar proflems, a huge JBL 4350 looms teach corner of the room. Even tisquawk boxes on the board arelot bigger than normal; they)made by Audio Shack in the Stateand despite their diminutive 14 exdiameter they can handle no le:than 25W rms apiece. They)driven off a compact 2 x 20W Sonamp mounted in the board, and tlt

system at full blast should b

capable of giving even the deaferproducer a sizeable headache.

Behind and to the right of thdesk, the recording equipmentgrouped. There are four machineand tucked forlornly away incorner is the smallest and oldesa 2 track Ampex of somewhtuncertain vintage. It's there if itneeded, but future users should lwarned that Roger doesn't likoperating it one bit. Two Stud(ASOs come next, one 2 track, anthe other 4 track. Both are hookeup to Dolby 361s. The 24 tracmachine is an Ampex MM116which has nothing but praise frotRoger, especially the tape transpoisystem. In fact the 1100 was som(thing of an offer that Koncouldn't refuse. It previouslbelonged to IES, a hire outfit, anit had only been used three times -so an asking price of £13 00(complete with an M24 Dolbsystem had to be a bargain, anwent a long way towards keepincapital equipment expenditurdown to an £80 000 target.

Rebuilding costs for the entir

44

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43

WORK

studio were in the region of £39 000,and the design work was handledby Peter Savory and Associates,an architectural practice which isgaining a considerable reputationin the recording industry. Thestudio environment itself is rela-tively long and narrow, but asRoger was surprised to find, itgives extremely clear separation.At the opposite end to the presentcontrol room is the site of the oldone. This is currently being con-verted to a general purpose record-ing area, which will be used foroverdubs, brass ensemble work,vocals and as an open drum trap-which should give the kind offairly live sound which many groupsare using currently. Also, at thetime we were there, the old screenswhich were rather suspect werebeing gradually replaced with pur-pose built Sonaplan units whichhave far superior acousticalproperties, according to Roger.

While intended primarily as arock studio, Konk is capable ofaccommodating up to 25 musicianswith ease, and it's fully ventilatedand heated so that there's a com-fortable working environment.Instruments in situ include a FenderRhodes, Yamaha piano, Hammondorgan and Leslie-and there'sgenerally some of the Kinks owngear lying around if its needed. Ifsomething else is required, Konktias an extremely good workingrelationship with Julianshire outfit. 'We needed a StudioFender Rhodes for one session,ordered it up and had it deliveredwithin the hour.' Equipment canbe loaded and unloaded withouttears and strained backs becausethere's a fully enclosed Transitsized loading bay, which allowsvans to be backed up virtually intothe studio.

Technical wizardry aside, one ofKonk's nicest features has to bethe bar and games room whichadjoins the studio. Most of thegroup were there waiting for theboard to be repaired, and a heateddarts game was in progress. It

certainly beats sitting in the corridorwith a lukewarm can of lagerclutched in a sweaty hand betweentakes. The bar stocks a compre-hensive range of alcoholic bever-ages, and while CAMRA wouldn'texactly be over the moon about thebitter, Roger pulled us a very pass-able pint with the sort of style thatonly comes with practice. Decoris authentic pub kitsch, circaKilburn, right down to the duckson the wall, buttoned velvetupholstery and Formica -clad bar.In a separate alcove, there's a full-size snooker table for the athleti-cally inclined. Apparently com-petition is fierce, and there was hotdebate as to who was the currentchampion among the Kinks. Allthe place needs for completeauthenticity is a blousy barmaid,a hint of sawdust on the parquetand a couple of drunken Irishmenin flat caps sleeping it off.

The new studio opened officiallyon July 23 1976, but pressure ofwork was such that sessions were

booked even before that date.Dick Emery was one of the firstpeople to record there, when he cuthis Christmas disc in July. Othernotables who've been in sinceinclude golden oldie Bert Weedon(`very professional-we mixed 11tracks in a single working day'),Mud, who did the overdubs fortheir next single at Konk, andCafe Society, a new group pro-duced by John Miller and ratedvery highly by Roger Wake. Whenthe Kinks are in doing albumsessions, they generally work twoto three days per week, but they'reusually prepared to work theirsessions in around other clients, tomake Konk a paying proposition.

At present Roger is the only full-time member of staff, but thechances are that he'll be getting ajunior in soon: 'now it takes about35 to 40 minutes to set up for eachtake, so it would be nice to have askivvy to take some of the workoff my shoulders and generallyhelp out around the studio.' He'sfairly certain that at £34 per hour,Konk probably offers one of the


cheapest 24 track rates, in theLondon area. This is another bene-fit of the Hornsey location, becausethe low overheads .can be passedon to the customer. 16 track is £32per hour, 2 and 4 track is £30 and,while the studio is available on a24 hour basis, there's a £5 per hourovertime surcharge after six in theevening.

When we left, the desk was finallyback in commission (after twohours of probing, much sage nod-ding of heads and dark muttersabout over efficient relays, thebother was traced to a single leakycapacitor!) and recording was justabout to begin-which seemed likea good cue for an exit from theoverworked look on Roger's face.The impression we had was of afriendly, well-equipped studio thatdoesn't maybe have the gloss ofsome of its West End counterparts-but seemed like a far nicerenvironment to work (and play) in.We certainly can't have been alonein this sentiment; at the time ofwriting the studio was healthilybooked up for quite some timeahead, which can't be bad.

Dave Hamill

Invisible SoundThere are two very surprising thingsabout A Chorus Line which openedsome months ago at the TheatreRoyal, Drury Lane. One is thefact that it actually lived up to allits advance publicity. Dedicatedto 'anyone who has ever danced ina chorus or marched in step . . .

anywhere', the show is a fascinatingchart of the agonising course of anaudition for a Broadway show,with a couple of dozen hopefuldancers giving of their best, tellingtheir life -story to the director andfinally being whittled down to afinal troupe. At the time of writing,a stream of hopeful British dancersis playing exactly the same role,for real, as they audition for partsin the British company which willtake over from the USA companywhen their work permits expire.

The second surprise is in thesound. I saw the show almost bychance and loved it, but foundmyself puzzling throughout theperformance about how on earththe voices of the cast could becoming over the house pa so loudand clear, cutting through theamplified pit band (hidden undera gauze roof to the pit) withoutever the sight of a mic or a hint offeedback. At first I was sure thatthey must all be wearing hiddenradio mics; but soon it wasphysically apparent that theyweren't. Then I wondered brieflyabout miming, but that, too, wasclearly a non-starter. Mics hiddenon stage? The stage set is a barerehearsal room, and there just isn'tanywhere to hide a mic. So afterthe show, all I could do was checkto find out who was organising thesound and phone them the nextday.

The show, as everyone by nowknows, was already playing simul-taneously in several US andCanadian cities before anotherperforming cast came over toEngland. Quite atypically for suchoccasions, the American importteam that arrived was fully rehear-sed and ready to go and was accom-panied by an army of techniciansand advisers, only a very few ofwhom turned out to be freeloaders.Autograph, the production soundengineers, were promised a fullsound system, and were naturallysomewhat surprised to find thatthe 'full sound system' was missingall cables and connectors. And asthey subsequently found out, nosingle shop in London can supply700m of cable off the shelf. Around£1000 was spent in Wardour Streetin a single day on connectors alone.Also, the imported communica-tions system, to provide a linkbetween the pit orchestra, off-stagechorus, lighting director and soundengineers, was of highly dubiousreliability. Obviously, the Ameri-cans already realised this, becauseeverything was duplicated, therebydoubling the cable requirements.It's now been replaced by a single,more reliable system. Even so,multiple multi -cores must snakeout over the theatre roof, to provideall the necessary links.

There was no sound cue -sheetavailable, quite simply becausethere are far too many sound cuesto write down, and no one couldpossibly look at the stage whilereading a sheet and working themixer controls.

So it was taught by word ofmouth and learnt by heart to under-stand why the cue -sheet is so com-plicated; you have only to look atthe method adopted of producingthe heavily amplified vocal sound

46

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45

WORK

frnm the rag,- on stage. withoutradio mics or miming used any-where in the whole show.

Along the front of the stage, atground level, there are mountedfive Sennheiser 802 hypercardioidmics, and slung over the stage,some 8m up, there are five Senn-heiser 816 rifle mics in one line oftwo and another of three. In thisway directional mics cover thewhole area of the stage. The micsare all wired through separatefaders on the mixing console which,following the old adage that theonly place you can judge audiencesound balance is from a seat in theaudience, takes up £30 -worth ofstalls seats every night. The mixedmic outputs are routed in mono viaAltec power amps to a bank ofeight Altec 9846A speakers, six ofwhich, weighing close on a ton, arehung in a cluster over the front ofthe proscenium. As the actorsmove about the stage, they are atany one time always in the line offire of at least one of the tendirectional mics. Every stage move-ment is rigidly pre -planned, andprovided the sound operator(Jonathan Deans, late of CoventGarden) knows his job (which heclearly does) it is possible to trackeach piece of dialogue or song atconstant level. But of course thedifficulties in practice are immense.Frequently there are several peopletalking or singing at the same time,unused mics must be killed to keepthe tracked sound uncluttered withbackground noise, and even theslight movement of an actor's headup or down can mean a differenceof several dB either way betweenmic channels. But, as anyone whopays a visit to A Chorus Line canfind out for themselves, the systemcan and does work. Although thishypercardioid mic technique hasbeen tried before, for instanceduring the West Side Story revival,it has never so far been reallysuccessful. This is because thesound level generated in thismanner has never really been ableto crowd out a stage band.

Although Autograph readilyacknowledge that putting the hard-ware together was relatively easy(as far as anything in the theatreis ever easy), one could write ashort book on the fine practicaldetails and problems. The deskused is a Trident Fleximix, aboutwhich everyone seems to have muchpraise, and which certainly seemsto have lived up to its name. Initialdelivery, from order, took twohours, and the mods to tailor it toA Chorus Line took another hour.A problem over providing thenecessary 48V phantom supply forthe Sennheiser mics was fixed nextday, and the desk layout currentlystands at 35 channels in, to sevensub -groups out. When the show isover, it will remain the property ofMichael White, the presenter, whoto his credit seems to have sparednothing to get the show on theroad without problems. The deskcan then be converted into two orthree separate smaller desks forfuture shows. The Altec speakersover the proscenium can be pannedor tilted and are fed by the Altecpower amps via an Altec 27 -bandroom equaliser. This takes somefairly hefty chunks out of thesound spectrum, eg above 3 kHz,both for eq purposes and to killthe possibility of feedback alto-gether. A similar mix fed to theAltecs over the proscenium is fedto a stack of eight Altec andElectrovoice speakers ranged roundthe circle and gallery rear, but witha 25 ms delay. Although all thestage sound is mixed as mono, the23 musicians in the pit are fairlyclose-miked and mixed into stereoat the desk, for reproduction alongwith the mono stage sound. In thisway there is a stereo spread of themusic with voices centre front.Mics used in the pit: two Neumann85s on the six woodwind, and twoElectrovoice RE2Os on the sixbrass. But as the pit musiciansstart putting deps in, as willinevitably happen as the run pro-gresses, internal section balance isbound to deteriorate. Doubtlessthere will then have to be moremics, closer to the players, so that


a sectional balance can be createdat the desk. So far the band micstake up 15 inputs on the desk. AMulti Ruutil Sin ing tutiulih vvliUunit is used for special effects only,never sweetening; the pa is other-wise totally dry. The total powerof the pa is 5.2 kW, the volume ofthe theatre being nearly 2 millioncubic feet !

In the covered pit, musicaldirector Ray Cook conducts withthe help of foldback from the stageand a closed circuit tv monitor,showing a view from the stalls.Similar foldback, via SennheiserHD414 phones, and a cctv monitoris available in the offstage chorusbooth, where an average of sevenor eight singers are picked up (instereo) and mixed into the bandand on-stage sound for chorusnumbers.

So far A Chorus Line has been asuccess story in the tradition of thehit shows like My Fair Lady andCamelot that preceded it at DruryLane. The first main hurdle to thefuture will be substitution of theAmerican cast with a British cast.No one can yet say how successfulthis will be. But so far seats arealmost unobtainable, and peopleare happy to buy (often fromscalpers) even those few behindthe sound mixing desk that thebox office will sell only with thedisclaimer that they have 'restrictedview'. But the sound engineersare still having to learn to livewith nightly taps on the shoulder.One night it was a little old lady.`Can you hurry up and finishfiddling with those knobs andmove out of the way before theshow starts?' she asked. The nextnight a precise German touristbegged Jonathan Deans 'to be sokind and move down in his seatby 1/ inches'. Just how he arrivedat this figure, rather than a roundinch or even two, is still puzzlingthe Drury Lane engineers.

Adrian Hope

Ron Geesin RevisitedSeveral years ago I intruded on thedecidedly un-ordinary world of Ron

Geesin, who was then working outof a studio at his home in LadbrokeGrove. As I found out when I cameW Wait lip thin Olwili Ger,inis, in many respects, a journalist'sWaterloo; you just can't sum himup pithily in an introductory para-graph. He's a musician, playingmore or less every keyboard andstringed instrument in his ownhighly individual, unclassifiablestyle; an electronics amateur; acreative recording professional withseveral short and feature film sound-tracks to his credit; a record com-pany with three 1p's; a publisherwith one book; and a performer oflive events even less easily classifi-able than his unclassifiable musicalstyles.

Shortly after the Ron GeesinUnlimited article that I finally puttogether, Geesin moved house toHeathfield, Sussex (home of a wildanimal park) into a farm -stylehouse that was then too smelly andgloomy for the locals to touch witha barge pole and is now every-body's dream escape from citypressures. I visited and found himstill impossible to sum up, stillbubbling with creative ideas, andstill (somewhat surprisingly, bear-ing in mind the hard world ofcommerce) managing to make ahappy living out of putting some ofthose ideas into practice. Theenthusiasms seem more ordered;he has for instance been makingsome KPM discs. But the sleevenotes are vintage Geesin. 'I presentsome tunes, untunes, anti -tunes,delightful and undelightful sounds,for all sorts of purposes, and statethat: the pieces herein displayedmay be combined with themselves(as much out of sync as possible) toachieve thicker, diffuse atmosphere,and playing things at differentspeeds would not be wrong!' pro-claims one. 'I introduce you to aworld of electronic sounds, shapesand rhythms created to enhanceand aggravate moving and un-moving pictures to startling effect',says the other. 'There is no point inbeing outgiving with ideas if thereis nothing into which to put theoutgivingness', he says in person,while explaining the need to savesome ideas for the future.

The present is financed both bypast royalties on recordings like thePink Floyd's Atom Heart Mother,in which he had an arranging hand,present book and record sales andthe music for a regular successionofcommercial films, such as the excel-lent BP series on the history ofmotoring. The old Revox G36shave been replaced by A 77s. Thenew machines are now being sub-jected to the same abuses as the old,a necessary part of the musical

48 *.

a question of ECONOMICS ?We manufacture what is generally called portable mixingdesks although for many applications are permanent fixtures.The facilities supplied and performance achieved are in noway indicated by the basic price. We offer these basic unitsnot to give on first sight a price advantage over our competi-tors, but as a genuine attempt to streamline production withits ECONOMIC and time -saving advantages.

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Basic Unit contains: Per channel, Line input andGain, HF and LF Eq, Two Aux Sends, one withpre/post, PFL, Pan, Channel routing, Ch fader.OUTPUT GROUP: PPM with line/monitor Sw,Oscillator, Switchable 40 Hz, 100 Hz, 1 kHz, 10 kHz,15 kHz, 2 Line/2 Monitor/2 Phones. Outputs +19dBm, Mono/Stereo Sw, Aux Return (echo),Tape/Line/PFL Sw, select on Monitor or Phonesoutput (Monitor mix 12/4 only). Optional Extras:Balanced Mic, Gram, Presence, Talkback, Limiter/Compressor, HF and LF Filters, 24v Power Supply.

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HSVI Audio Voltmeter. Average reading £125.00HSV2 Audio Voltmeter. True r.m.s. reading £175.00AN M I Audio Noisemeter. Average reading £150.00AN M2 Audio Noisemeter. True r.m.s. reading £200.00

Four instruments are now available for the measurementof audio frequency signals including noise. They are derivedfrom a basic battery operated voltmeter design having 16measurement ranges from I ()RV for full scale meter deflectionto 300 V f.s.d. The Voltmeter has a high input impedance andlow inherent noise. It is fitted with a high grade meter havinga 5" mirror scale of excellent linearity, calibrated in voltsand dBV.

The audio Voltmeter (HSVI) becomes an Audio Noise -meter (ANMI) by the inclusion of frequency contouring net-works having characteristics recommended by internationalorganisations concerned with specifications and measure-ment standards, as being suitable for the quantitative measure-ment of the subjective effect of noise in audio systems. TheHSVI and ANMI instruments respond to the average ormean value of the waveform being measured and are cali-brated in r.m.s. values on a sine wave.

In the HSV2 and ANM2 instruments an r.m.s. to d.c. con-verter module is incorporated which provides a true r.m.s.reading on waveforms with a crest factor in excess of 10.These instruments are also provided with an additionaloutput socket giving 1.00 V d.c. output corresponding to1.00 V at nominal full scale meter deflection to operate achart recorder or d.c. digital voltmeter.

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47

WORK

formula for instant overdubbing;this is essential to Geesin's musicaland recording technique. It's damn-ably clever, horribly difficult to putinto operation, and is even nowonly occasionally copied - forinstance by Queen in fairly primi-tive fashion on their Night At TheOpera 1p.

When listening to the fmal results,it's only too easy to forget that theonly multitrack recorder in sightis a Teac 4 -track. Everything isdone in stereo, often mono subse-quently tricked up one way oranother to produce a stereo effect,and stored in 'slabs' on the Teac orseveral Revoxes running in sync forshort periods. In its simplest form,the system relies on running a reelof tape from the take -off spool ofone machine through the heads ofthat machine (set in the 'record'mode) and from there, not onto therecorder's take-up spool butthrough the heads (set in the 'play-back' mode) of another Revoxalongside it, using that machine'stake-up spool. In this way the sametape runs first through the recordhead of one machine and then, aftera delay determined by the spacingbetween the two machines, throughthe playback head of the othermachine. Geesin feeds a soundsignal, for instance by direct injec-tion from an electric guitar, througha mixer onto the tape runningthrough the first batch of heads.

In this way the injected sound isrecorded onto the tape and after thesubstantial delay inevitably imposedby the spacing of the two machines,the recorded sound is played backby the heads of the second machine.Audible reproduction is either overloudspeaker monitors or head-phones and at the same time themixer feeds the reproduced signalback to the first set of heads, tore-record it on the tape. Thus asingle note will in this way berecorded on the tape as a repeatedsuccession of exactly similar singlenotes, spaced by the fixed delaygoverned by the separation of theheads of the two machines.

Because the delay is considerable,the repeat may be of a musicalphrase and the mixer enablesGeesin to add another, differentphrase to it and another, andanother and so on. Thus in practicea simple bass line can be laid downby recording it on the first set ofheads, heard as it passes throughthe second set of heads and fedback to the first set of heads again,along with a matching melody line.It sounds easy; but it's not. Themain difficulty is in matchingrhythm to delay so that each newphrase is in sync with those already

being recycled. Geesin has nowmastered the technique to such anextent so that within a matter ofminutes, a musical (and I emphasisethe word musical to distinguishfrom garbled musique concrete)orchestration can be built up in thetime it takes for a reel of tape torun through the machine. Indeed,if one had to pick on a singlereason why Geesin succeeds whereothers fail in the same field, it wouldbe his ability at one and the sametime to handle electronics, composemelodic tunes and maintain rigidtempi.

Electronics, along with all hisother do-it-yourself activities, suchas photography, metal and wood-work were learned the hard way.`No one taught me; I'm doing it bydoing it', he says. Geesin's abilityto write catchy tunes is doubtless agift, but a cultured gift, neverthe-less. Plenty of those blessed withthe ability to write melodies gradu-ally decide it is beneath their dignityto do so. And the need for a goodsense of rhythm? Well try for your-self the almost impossible task(which Geesin's delay techniquerequires) of tapping in time withsingle beats spaced all of eight ornine seconds apart !

The basic delay system isobviously under continual modifi-cation. When I arrived, Geesin hadjust finished making an extensionarm, around which the tape is ledbetween machines, with an oldRevox stereo replay head at theapex of the triangular path whichthe tape is thus constrained to take.The head is on a swivel, and feedsback to the mixer. Swivelling thehead alters azimuth; therebycausing phasing.

I noticed another Geesin gadgetin the process of development. It'sa mechanical -electrical rhythmmachine which is really a cleverupdate of the old style of music box.A gramophone turntable can carryany one of a whole range of metalplatters (based on the aluminium


cores stripped from old acetatemasters) and into which rings ofperforations have been stamped atregular intervals. On one disc thecircumference is divided into elevenequal cake -like slices of perfora-tion; on another disc twelve, andso on, up to thirty-one. Pins can beplaced in these perforations, inchosen patterns to provide a porcu-pine disc like that of a music box.A pressure -sensitive pickup, forinstance a gramophone cartridgeor contact mic is then held abovethe disc as it rotates so that thepins strike the transducer in a con-tinuous rhythm, dictated by thespacing of the pins. If severaltransducers and several rows ofpins are used on each disc, theyproduce variations of sound, eachin different rhythms but all withinthe same basic metre, as dictated bythe number of divisions on the disc.Even in its primitive prototypeform, the gadget was able to pro-duce instant jungle drums, andcreate time and tempi that wouldmake even the most modern jazzdrummer wince at their impos-sibility.

All this isn't meant to replacemusicians. It's simply another partof Geesin's scheme to make himselfever more musically independent.This is highly necessary if you workfrom the depths of Sussex, whereyou are likely to be snowed up inthe depths of winter, with a dead-line for a film soundtrack tape.

Also on do-it-yourself self-suffi-ciency basis, Geesin appears to begrowing enough vegetables toweather a siege, publishing anddistributing his own books andrecords, coping with mundanemiseries like VAT, and even findingtime to write two -page rude lettersto the French RCA Black -and -White record label. Geesin's keenerthan average rhythmic ear detectedthat, in re -issuing cleaned -up ver-sions of old jazz recordings, thecompany had erased clicks andpops by physically removing seg-

ments of tape. Geesin's answer,gleaned from his friend J R T Davies(`upholder of quality in re -issueprograms' he explains) has obvi-ously never been heard of inFrance. 'What you do', he says, 'issimply scratch off a little of theoxide at the point on the tape wherethe click appears. That way youbloop out the noise withoutaffecting the rhythm.' The partlypuzzled, and partly offended pro-ducer recently rang him fromFrance. It remains to be seenwhether future Black -and -Whitere -issues are rhythmically sound.

Summing up and rounding off aGeesin piece is as difficult aswriting an introduction. I can't dobetter than quote a couple ofunrelated comments verbatim,because together they do the trick.

`A man's got to use all hisenergy . . . the secret of creativity isto use all your energy' and 'What Iwant to do is innovate-not go onOpportunity Knocks and talk aboutit-just innovate, be challenged andcontinue.'

Adrian Hope

agony Musicians' humour tends to bethe same the world over. The cruiseliner docked for a day at a tinyport in Alaska and the multi-national band resident on boardexplored the one-horse town. Mainstreet sported a bar, bank, barberand general store. Everywhere youlooked there were snow-cappedmountains. 'What could you doin a place like this?' said onemusician, as they killed time beforesailing. 'Open a bassoon repairshop?' said the other, without amoment's thought.

The radio play recording wasgoing well, but the beheading scenewasn't quite to the producer'sliking; he felt that cutting a cabbagein half sounded like . . . cutting acabbage in half. At the directionof the studio effects manager, apig's head was duly brought inand, with some difficulty, theyhacked it in half; first with aneffects sword and when that didn'twork, a fireman's axe.

A mutilated pig's head is not theeasiest of things to dispose of, evengiven the ingenuity of this produc-tion team. It was therefore prob-ably pure coincidence that brawnappeared on the canteen menu thenext day.

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MUSTANGCOMMUNICATIONSNelson Street, Scarborough,North Yorkshire Y012 7SZEnglandTelephone 0723-63298 2

GRAHAMSOver the years we have established a reputation forproviding both comprehensive knowledge and facili-ties, allowing customers to choose for themselvesfrom the most sophisticated domestic and semi -prosound equipment. We are extending our activities toinclude a new showroom based on the Teac CreativeCentre, with much to interest the serious amateurand budget conscious professional.

If you are looking for recorders (stereo or multi-channel) DBX, Dolbys, Mics, stands and accessoriesand want help in choosing the right machine for you:

Come in and listen

GRAHAMS88 PENTONVILLE ROAD, LONDON, NI.

01-837 4412

r RADFORDAUDIO MEASURING INSTRUMENTS

LDO3. LOW DISTORTION OSCILLATORA continuously variable frequency laboratory oscillator with a range10Hz-100kHz, having virtually zero distortion over the audio frequencyband with a fast setting time.Specification:Frequency range:Output voltage:Output source resistance:Output attenuation:

10Hz-100kHz (4 bands)10 volts r.m.s. max.150 ohms unbalanced0-100dB (eight, 10dB steps plus 0-20dBvariable)

Output attenuation accuracy: 1%Sine wave distortion: Less than 0.002% 10Hz-10kHz (typically

below noise of measuring instrument)Square wave rise and fall time: 40/60 n.secsMonitor output meter: Scaled 0-3, 0-10 and dBVMains input: 110V/130V, 220V/240VSize: 17" (43cm) x 7" (18cm) high x 81" (22cm)

deep £300.00

LDO3B. LOW;DISTORTION:OSCILLATORAs LDO3 but additionally fitted with output amplifier and transformerproviding a 600 ohm floating balanced output. Unbalance: -80dB1kHz, -60dB 10kHz. Distortion less than 0.003%. 30Hz-20kHz.

£400.00

DMS3. DISTORTION MEASURING SET(illustrated above)A sensitive instrument with high input impedance for the measurementof total harmonic distortion. Designed for speedy and accurate use.Capable of measuring distortion products down to 0.001%. Directreading from calibrated meter scale.

Specification:Frequency range:Distortion range (f.s.d.):Input voltage measurement

range:Input resistance:High pass filter:Power requirement:Size:

5Hz-50kHz (4 bands)0.01%-100% (9 ranges)

50mv-60V (3 ranges)47K ohms on all ranges12dB/octave below 500Hz2 x PP9, included17" (43cm) x 7" (18cm) high x 81" (22cm)deep £250.00

Send for leaflets for further details:

Radford Laboratory Instruments LtdASHTON VALE ROAD, BRISTOL BS3 2HZ, AVON

Tel 0272 662301

!wimpsRadford low distortion oscillator

MANUFACTURER'S SPECIFICATIONFrequency range: 10 Hz -100 kHz (four bands).Output voltage: 10V rms maximumOutput waveform: sine and square.Output attenuation: 0-25 dB potentiometer and+20 dBV to -80 dBV in 10 dB steps.Output source resistance: 151 ohms constantfrom 0 dBV to -80 dBV, 147-154 ohms at +10 dBV,and 100-177 ohms at +20 dBV with 25 dB change of0-15 dB potentiometer.Sinewave distortion : 0.002% mid audio band.Typically 0.001% rising to 0.005% at 10 Hz and100 kHz.

Hugh Ford

Squarewave rise and fall time: 50 ns.Output monitoring: 102 mm mirror scale meterengraved: 0-1, 0-3.2 and 0 dBV to -15 dBV (1V-0dBV).Calibration accuracy: 1% fsd.Power source: 110V, 120V, 130V, 220V, 230V, 240V,40-60 Hz, ac.Overall size: 430 x 178 x 230 mm.Weight: 7.2 kg nett.Price: £300 Standard version.

£400 600 ohm balanced version.Manufacturer: Radford Instruments Ltd, Bristol,England.

MUCH modern audio equipment has har-monic distortion specified in the third

decimal place and one really does wonder howthe manufacturer manages to make themeasurements with any confidence, for to myknowledge there are only two makes ofoscillator commercially available which haveany hope of giving meaningful measurements.

The first on the scene was the Radfordwhich has been about for many years andnaturally used valves, but Arthur Radford hasof course now caught -up with things in theform of the new Series 3 Low DistortionOscillator, which is of course a completely`solid-state' instrument.


Two versions of the instrument are available:the standard version has an unbalanced 150ohm output and the B version offers a 600 ohmbalanced floating output, in addition to thepossibility of a 300 ohm floating output or a150 or 300 ohm unbalanced output. As is tobe expected the distortion performance of thebalanced output is restricted by the additionof a drive amplifier and transformer, but aswill be seen the performance is remarkablygood.

The presentation of the instrument is a blackcrackle case with an alloy front panel withclear legends in black. There is a 11.5 cmdiameter frequency tuning dial which covers

one decade and operates in conjunction witha four -position range switch, thus coveringthe total range 10 Hz to 100 kHz.

Signal output level is controlled by an 11 -position 10 dB step attenuator covering 0.1 mVto 10V maximum outputs which are incremen-ted by a potentiometer which has in excess of20 dB range. The actual open circuit outputlevel is indicated by a meter scaled in volts anddBV and which is equipped with an anti -parallax mirror. Three outputs are available,a fixed level unbalanced output at a BNCsocket, the attenuated unbalanced 150 ohm or300 ohm output at a second BNC socket andthe balanced output. This comprises a floating600 ohm centre tapped output at spring -typeterminals and an extra terminal which isconnected to earth.

The remaining front panel facilities comprisea green incandescent power indicator lamp andfour pushbutton switches. The top one ofthese is the power on/off switch below whichthere is a sine/squarewave output switch and anon -locking 'oscillator off' switch which is avery useful feature. The fourth switch controlsthe output routing to nominally '150 ohmsunbalanced' or '600 ohms floating'. Howeverit does not isolate the unused output and thiscan create problems.

At the rear of the instrument there is thefixed mains lead (I prefer IEC connectors) andthe voltage selector. In addition, there is the20 mm power fuse the value of which is aclosely guarded secret! The technical instruc-tions provided give component values, circuitsand servicing information but nothing aboutthe mains fuse.

The standard of components and printedboards used in the construction is excellent,and should board replacement ever be needed,this is a very simple matter as all connectionsare by slide -on tags. However, the instrumentsuffers from my bete noir, the knobs fall offthe rotary switches because the shafts do nothave flats and single screw fixing is used.Another small grumble is that there is notilting foot arrangement which can make themeter awkward to read.

DistortionThe prime quality of the Radford Low

Distortion Oscillator is that, while to myknowledge there may be one equal, there iscertainly no better commercial oscillator sofar as distortion is concerned in the audiofrequency band.

Reference to fig. 1 shows that the thirdharmonic distortion at the unbalanced outputis over 100 dB down on the fundamental(0.001 % distortion) over the frequency band20 Hz to 15 kHz and that the second harmonicis not far short of this fantastic performance.The testgear required to measure individualharmonics at these low levels (with a 20 dBmargin) unfortunately did not function outsidethe band 20 Hz to 20 kHz, so fig. 1 includesspot checks on the total harmonic distortionand noise at 10 Hz, 20 kHz and 50 kHz but inthese instances the margin in hand with thetestgear affects the results, all of which relateto +20 dBV output (10V rms).

Perhaps even more remarkable is theperformance of the floating balanced outputwhen driving a 600 ohm load with 5V rmswhich is the maximum output into a matchingload. This performance is shown in fig. 2

FIG. I RADFORD LDO AT UNRA1 ANCED OUTPUT014

.0007

.006 /.

004%

+TOTAL HARMONIC 8 NNSE-SECOND HARMON C--HURD HARMONIC

002%

dim

20 50 100 200 500 16 2K

FREQUENCY IN Hz

5K 10K 29K SOK 1006

which shows the expected distortion introducedby the balancing transformer, but a totalharmonic distortion of less than 0.002 % from60 Hz to 7 kHz is an achievement whichdeserves applause.

Noise in the output was also respectable at-107 dB over the band 20 Hz to 20 kHz withmains hum being greater than -120 dB.Investigations into the square wave perform-ance showed that there was no overshoot ortilt or ringing at the unbalanced output whichhad a rise and fall time of 55 ns irrespective ofthe oscillator frequency.

The 'maximum output' connector has aslower rise and fall time at 100 ns and it waswhile investigating this output that a fault wasfound to occur. At frequencies below 80 Hzthere was a tendency for the edge of the squarewave to become unstable for a period of around60 µs as is shown in fig. 3. This fault was notapparent in a second sample of the oscillatorwhich was a modified version submitted as aresult of this and other faults which werefound.

FIG. 320usjcliv, 40 Hzspurious oscillation onsquarewave, 40 Hz, 20 µs/div

of about 0.4 dB occurring at the high end ofeach range, as is shown at the top of fig. 4.However at low output settings of the attenua-tor, the unbalanced output suffered from leak-age at very high frequencies, this becomingreally serious on the -80 dB range the upperdecade of frequency being shown in fig. 4 forthe -70 dB and the -80 dB attenuator settings.

The performance of the balanced output atmaximum output level into 600 ohms is shownin fig. 5 which, again demonstrates the peakingat the upper frequencies of each range, but asis to be expected from the transformer outputthe very high and very low frequencies roll off,but not to an excessive extent. However, as isshown, the response depends upon outputlevel!

Frequency dial calibration was generallywithin 2% of nominal, but this did not holdon the upper frequency range where 10 kHzindication was 9.82 kHz, 30 kHz was 29.3 kHz

FIG. 2 RADFORD LDO TOTAL HARMONIC DISTORTION & NOISEBALANCED OUTPUT

LOADED 6000 AT

MAX OUTPUT

006%

-006

-004%

002%

10 20 9) 100 200 500 1000 2KFREQUENCY IN Hz

56 100 20K 506 TOOK

Frequency response and calibration and 100 kHz was actually 92.4 kHz with aThe flatness of the oscillator at maximumgenuine 100 kHz being available off the end ofoutput was generally reasonable with a boost the scale. 52

, RADFORD L.D.0FIG. 4 ATTENUAJOR OUTPUT FREQUENCY RESPONSE -SEE TEXT

.2048.

-80dBv

113

20 50 1CO 200 500 1K

FRECOENCY IN Hz

?X 510 10K ?OK 50K 100K

51

RADFORD LOW DISTORTIONOSCILLATOR

Attenuator and outputsThe attenuator accuracy for each 10 dB step

at 1 kHz is shown in fig. 6 in terms of incremen-tal accuracy and individual step accuracy. Thestep accuracy can be seen to be very good witherrors only in the order of 0.04 dB, but this isunfortunately cumulative and added up to a0.4 dB error from maximum to minimumsetting.

This is a shame because the accuracy of themeter at full-scale deflection at maximumoutput was really excellent and within thewidth of the narrow pointer and also as goodas it could be at 30 % full-scale deflection.

It is possible to hold a long debate aboutthe meter scaling: clearly we want the excellentvoltage scale which is provided, but thequestion of whether the dBV scale is the rightone as opposed to a dBm scale is largely amatter of personal taste. It is understood thatRadford will offer an option, but I believe thatthe vast majority of engineers work in dBmirrespective of the loading which should ofcourse be 600 ohms for the dBm to be strictlymeaningful !

The output impedance of the 600 ohm

balanced output was found to be 606 ohms onthe 0 dBV range and below, rising to 611 ohmson the -L10 dlIV range and to 644 ohms onthe +20 dBV range. Operation of the variableattenuator did not have any effect upon theseimpedances, but I feel that the manufacturercould make the change of output impedanceclearer in his literature. As is to be anticipated,the use of half the balanced output as a 300ohms floating output has similar outputimpedance characteristics.

While the attenuator output has constantimpedance of either 300 ohms or 150 ohmsnominal, the output is clearly identified '150ohms source' when in fact it has a 300 ohmssource impedance unless a link is inserted tojoint the 'outer' connections of the floatingoutput-I regard this as confusing as we allknow that people do not read instructionbooks!

The output balance was found to be betterthan Radford's specification, being 65 dB at10 kHz, 84.5 dB at 1 kHz and 106 dB at 100 Hzas measured with 300 ohms between the centretap and each outer of the output with theunbalance being measured across 600 ohmsbetween the centre tape and earth.

The internal meter claims to be averagereading calibrated in terms of rms, and I have

RADFORD L Da,FIG. FREQUENCY RESPONSE OF 600n. OUTPUT WHEN FULLY LOADED

1d6

AT .10dv OIJIPUT

5 10 20 50 100 200 500 1K

FREQUENCY IN Ni

2% 5% 10% 20% 50% 100K

fFIG.6 RADFORD LDO AT TENUATOR ACCURACY

AA

K

K

0

KW

+ K 4-K

+ + + 4-I- + 4. S.

.10 0 -5 -20 -30 -40 -60 -60 -70 -80 d8

1.0-1d8

X CUMULATIVE ERROR

+ STEP ERROR


no grumble about this so far as sinewaves areconcerned, but with squarewaves the meter isintended to indicate the rms value but wasfound to indicate 10/0 too low.

A further peculiarity was that the meterappeared to suffer from leakage at highfrequencies, in that on all output voltage rangesat 100 kHz with sinewaves the meter spuriouslyindicated 10 % of full-scale irrespective of theposition of the fine output level control, andeven worse with square waves to the extent of62 % Ipurious full-scale deflection. These faultsdue to leakage had virtually disappeared in thesecond modified sample of the oscillator whichwas submitted by Radford.

Other mattersInvestigations into the frequency stability

showed that there was a warm-up drift as isshown in fig. 7 which demonstrates an initialdrift of six parts in 106 per hour which isroughly twice that shown in the manufacturer'sliterature. After warm-up, the drift patternbecame rather erratic with drift varyingbetween two parts in 106 and 14 parts in 10'over five-minute periods.

These orders of stability make distortionmeasurement using a tuned notch filter rathertiresome, as it is impossible to retain theoptimum balance without continuous knobtwiddling with these orders of frequency drift.Furthermore, the oscillator frequency wasrather sensitive to vibration, such that lightlytapping the instrument's case produced anundesirable frequency shift.

SummaryIn terms of distortion performance this is a

most excellent oscillator at a reasonable price,but it is let down by a large number of short-comings in other directions. Giving creditwhere credit is due, Radford quickly submitteda second modified version of the oscillatorwhich had added screening in the area of theattenuator and meter amplifier. This sampledid not suffer from attenuator leakage or meterleakage and the low frequency squarewaveproblem did not exist.

It is understood from Radford that thesefaults are peculiar to the balanced outputversion of the low distortion oscillator, andthat all future production will be modified. El

FIG.7 RADFORD LDO WARM UP DRIFT

1 PART 10104

10 MINUTES

EVENTIDE CLOCK WORKSANNOUNCE THE U.1

MODEL,H HID

11115

'INPUT LEVEL FEEDBACK HARMONIZER

1, 0

PITCH RATIOP100.1- 13110.AV 30 30 OUYPOT A

11111111111111111111 11111111=1111onn, 5 As OCI 7.5 15 30 30

MANUAL ANTI -FEEDBACK

MAN N,50 CV

111111111MMPI I CH CONTROL. Ur F.C,

41,

EVENTICIECLOCK WORKS

POWEP

0

PITCH CHANGERThe HARMONIZER employs digital circuitry andRandom Access Memories to actuallytranspose input signals by up to a full octave upor down. Unlike the so-called "frequencyshifter" which creates dissonances, theHarmonizer preserves all harmonic ratios andthus musical values. Any musical interval can beachieved by the continuously variable control,and an optional monophonic or polyphonickeyboard allows real-time "playing" of theHarmonizer, so that the musician canharmonize with himself.

DIGITAL DELAYThe HARMONIZER is a low-cost, very versatiledigital delay line. The delay is variable in7.5 ms steps up to 112.5 ms ; a second output isoptionally available that varies up to 82.5 ms.

ANTI -FEEDBACKFeedback caused by energy build-up due toroom resonance is decreased by shiftingsuccessive repetitions of the same signal awayfrom the original frequency.

SPECIAL EFFECTSIt can be used to speed up and slow down tapeswithout affecting pitch. It can create some of thewildest effects on record!

Feldon Audiolts1 Dept SI126 Great Portland StreetLondon W1Tel: 01-580 4314Telex: 28668

r RADFORD'AUDIO LABORATORY INSTRUMENTS

for the professional

LDO3.B Low Distortion Oscillator,balanced outputA LDO3 but fitted with an output amplifier and screened balanced transformerproviding a 600 ohm floating/balanced output, and 150 ohms unbalanced output.

DMS3 Distortion Measuring Set (illustrated)Measures total harmonic distortion down to 0.001% speedily and accurately.Direct reading from calibrated meter.

HSV I High Sensitivity VoltmeterAs HSV I but true r.m.s. reading.

ANMI Audio NoisemeterAn accurate voltmeter and noisemecer with 16 ranges. lOuV-300V f.s.d. Fittedweighting characteristics. Wide band, DIN Audio Bank, IEC/DIN Curve 'A'and CCIR. Average responding.

ANM2 Audio NoisemeterAs ANMI but true r.m.s. reading.

ANFI Audio NoisefilterAn active filter to CCIR weighting characteristic for use with external voltmeter,(Ref. Dolby Laboratories Inc., Bulletin No. 43, Mar 76).Also in stock: All Radford Speaker drive units and crossovers and B & N/Radford monitor loud speaker systems.

LDO3 LowDistortionoscillatorA continuously vari-able -frequency lab-oratory oscillatorwith a range 10Hz-1.00kHz, having vir-tually zero distortionover the audio fre-quency band with afast settling time.

HIGH PERFORMANCE AMPLIFIERSfor the enthusiast and professional

ZD22 Stereo Pre -amplifier Control UnitA stereo pre -amplifier of virtually zero distortion. Inputs for disc, tuner andtwo tape machines, providing comprehensive recording and reproducingfacilities. Sensitivities: Disc I mV, and Auxiliaries SOmV., for IV output,Exceptional signal/noise ratio. Output at clip level I 8V r.m.s.

ZDIOO Power AmplifierA stereo power amplifier of all aluminium construction with high thermal massand designed for continuous operation at high output level. Provides 150watts per channel into 4 ohms and 90 watts per channel into 8 ohms at virtuallyzero distortion

HD250 Stereo Integrated AmplifierUses ZD22 pre -amplifier with a power amplifier having a power output inexcess of SOW per channel into 4-8 ohms. Distortion less than 0.02% at ratedpower, typically less than 0.01%. True complementary symmetry output.Headphone output. Inputs: Disc tuner, and two tape machines.

ZD22, ZDI00. HD250 are available from stock.

Available soon: ZD5O (110 w.p.c./4 ohms, 70 w.p.c./8 ohms) and ZD200 (250w.p.c./4 ohms, 150 w.p.c./8 ohms).

Your Radford Dealer

SWIFT OF WILMSLOW 5 SWAN STREET, WILMSLOW, CHESHIRE (TEL: 26213)Mail order and Personal Export enquiries:-Wilsmlow Audio, Swan Works, Bank Square, Wilmslow. (Tel: 29599)

53

Radford distortion measuring setHugh Ford

it)

MANUFACTURER'S SPECIFICATIONFrequency range: 5 Hz to 50 kHz (four bands).Distortion per cent range: 0.01% fsd to 100% fsd.Attenuator accuracy: 1%.Input voltage range: 50 mV to 50V. Three ranges50 mV to 0.5V, 0.5V to 5V and 5V to 50V (50 mV to0.5V range not operative on 0.01% and 0.03% fsdranges).Second harmonic attenuation: 0.5 dB.Frequency response bandwidth:250 kHz (-1 dB).High pass filter: 500 Hz (12 dB/octave).Input resistance: 47k ohms.Meter:101 mm mirror scale engraved 0-1, 0-3.16 fsd.dB and battery check-rms reading to crest factorof 3.Power source: 2 x PP9 batteries (included).Size (whd): 430 x 178 x 230 mm.Weight: 7.5 kg, 11 kg packed for transport.Price: £250.Manufacturer: Radford Instruments Ltd, Bristol,England.

THE Radford Distortion Measuring Set isof course intended as a companion to the

Low Distortion Oscillator, and as such has asimilar form of mechanical and electricalconstruction. As with the oscillator, theprinted boards and components are to thehighest standards and the overall presentationis good.

An interesting point about the distortionmeasuring set is that it operates from two 9 -voltPP9-type batteries drawing less than 7 mA fromeach battery. Such a low current means thatthe batteries should have an extremely longlife, but when the time does come to changethe batteries it is a fairly long-winded operationinvolving the removal of four slotted screwsand seven Phillips screws !

The advantages of battery operation are theloss of mains hum problems, and more import-ant, the fact that there are no longer anyground loop problems when measuring distor-tion of power amplifiers-that is provided thatthe oscilloscope monitor output is used withcaution.


4

Battery condition is checked by depressinga front panel switch which activates the frontpanel meter if the instrument is switched on,thus battery condition is-as is only sensible-checked on load. The meter has a green sectorfor the battery check, and three scales 0-1,0-3.2 and a decibel scale from 0 to -15 dB.

These scales cannot, as would be useful, beused as voltage scales because there is novoltage calibration; therefore a separate volt-meter is essential for normal work. Input levelis controlled by a 3 -position range switchwith nominal level capability from 50 mV to50V in conjunction with a concentric poten-tiometer for setting the 100% level on themeter in association with a 'set fsd/readdistortion' pushbutton.

Distortion in the form of total harmonicdistortion is read from the meter by using the9 -position 'distortion range' switch whichcovers full-scale deflections from 100% distor-tion down to 0.01 % distortion in 10 dB steps.

Nulling of the fundamental is done by a

twin T -network with feedback, the tunedfrequency being selected in four ranges by arotary switch and the fine frequency beingtuned on a large diameter dial which coversone decade, the total instrument range beingthe four decades from 5 Hz to 50 kHz. Theultimate balancing of the network is done withthree sets of dual concentric controls whichhave coarse, medium and fine action-the latterbeing none too fine when measuring very lowtotal harmonic distortion.

The only remaining operator control is apressbutton switch which inserts a 500 Hz high-pass filter for reducing the effects of hum andnoise when measuring the total harmonicdistortion of signals above around 1 kHz.

The input and also the distortion residualoutput are by means of single -ended BNCconnectors at the front panel, which is blackanodised with very clear legends. However, asthe two lowest distortion ranges of 0.01 % and

0.03 % fsd do not operate with the input levelswitch on its most sensitive range of 0.05-0.5V,I would have liked to have seen this indicatedon the front panel, as the likes of myself justpick up an instrument of this type and driveit without reading the instruction book.

PerformanceProbably the most serious error in many

distortion meters is due to the rejection notchbeing too broad and thus lowering the level ofsecond and higher harmonics which we wishto measure. Fig. 1 shows the overall frequencyresponse of the Radford instrument when it istuned to reject 5 Hz. It should be noted thatthe second harmonic at 10 Hz and higherharmonic frequencies are within ±0.2 dB,which is a very good performance. At the highfrequency end, the -1 dB point is at about 120kHz and as will be seen this is a cause forcomplaint.

Reference to fig. 2 shows the curves for thenotch filter at 10 Hz, 100 Hz, 1 kHz and 10 kHz,it being seen that at all but 10 kHz the attenua-tion of the harmonics is less than the specified0.5 dB by a very good margin. However, at10 kHz we have a curve which attenuates thesecond harmonic by 1.2 dB and the 3rd, 4th,5th and 6th harmonics by 1 dB. While thisperformance is not bad by many standards itis not to specification, and similar results wereobtained at 20 kHz and 40 kHz notch frequen-cies. 56 00-

,r RADFORD DISTORTION SET OVERALL FREQUENCY RESPONSE MEASURING DISTORTION AT 5F

10 20 so 1E0 210 500 1000

FREQUENCY IN Hz

1K 50 10K 20K 5 K 1000

Some ofour customers'ordersdrive us completely round the bend.

tft4

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1,-tif$f$ftl,rrff"0 ,, /f,,,,

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There are very few limits to whatwe can do with our Series 2 mixer.

Usually we can modify it to suitalmost any studio, and any customer'srequirement.

We can make it bigger, build in patchbays, LED VU/PPM metering, sweepableequalisation, remote switching, oranything else you ask for.

And even without modifications, theSeries 2 is a highly versatile mixer withimpeccable specifications. (Each modelis made individually and by hand tomake sure that the specifications staythat way.)

The Series 2 comes in sixstandard versions: 12/4; 12/8; 16/4;16/8; 24/4; 24/8.

In every model, each group outputhas dual track switching so, for example,an 8 -output console can be hooked upto a 16 track recorder without anyrepatching. And there are direct lineoutputs from each input channel, eitherpre- or post -fade, so that you can use arecorder with as many tracks as themixer has inputs.

Used together, these two featureslet you make multitrack recordings withsimultaneous stereo reduction.

And what's more, all this versatilitywon't cost you the earth.

The straight Series 2 mixer.It's portable, and can be supplied

with an aluminium flight case.

For more details, contact:Soundcraft Electronics Limited,5-8 Great Sutton St, London EC1V OBX.England Telephone: 01-251 3631.Telegrams: Soundcraft LDN [Cl.

UUMEPifiFT..jELECTRONICS LIMITED

AES PARIS DEMO ROOM D 05

RADFORD DISTORTIONMEASURING SET A,

The performance of the 500 Hz high-passfilter is shown in fig. 3, which demonstratesthat it acts at the correct frequency and itseffect is minimal above 1 kHz.

The accuracy of the dial indication of tunedfrequency was generally within ±2 %, such thatthe dial can be used as a rough frequencymeter. More important, the accuracy of thedistortion range attenuator was within +0.08-0.12 dB cumulative error over its entire rangewith a worst case incremental error of 0.2 dB-a very satisfactory performance, as shownin fig. 4.

Efforts to measure the maximum fundamen-tal rejection were hampered by the instabilityof the instrument when used on the mostsensitive range of 0.01 % total harmonicdistortion full scale. However a 16 dB marginbelow 0.01% was achieved at all frequencies,this being equivalent to a residual of only0.0015 % total harmonic distortion with inputsabove 0.5V. The actual indicated residual noisewithout any input was 0.0018 % equivalentdistortion without the high-pass filter in circuitor 0.0012 % with the filter in circuit.

In practice when using the companionRadford Low Distortion Oscillator or mylaboratory oscillator, the residual distortionwas found to be less than 0.002 % below 20 kHzand to be limited by the Radford oscillator athigher frequencies. Measuring such low levelswas tiresome, particularly at high frequencieswhere the balance of the distortion meter wasnot only very critical, but drifted. Also, theinstrument was microphonic such that evenabrupt operation of the distortion range switchcompletely upset the balance. However this isnot an unusual complaint with this type ofinstrument-you just have to be gentle and notthump the bench in frustration, or you startagain !

On the input end, the required input levelfor use on the most sensitive distortion rangeswas 0.517V at 1 kHz with the ability to handle50V which is adequate for most power amplifierapplications. On the most sensitive inputranges where the 0.01 % and 0.03 % distortionranges are not available for use, the inputsensitivity was found to be 50.6 mV which is

FIG.2 RADFORD DISTORTION NOTCH RESPONSES

FIG. 3 RADFORD DISTORTION SET HIGH PASS FILTER

close to specification.The input impedance was adequately high at

between 55k ohms and 65k ohms in parallelwith less than 20 pF at any input sensitivitysetting. The distortion output offered IV rmsfor full-scale meter deflection from a sourceimpedance of 2k ohms.

While some manufacturers use an averagereading meter, I was pleased to note that thisinstrument has a genuine rms detector as is

FOR MONITORING MONO OR STEREO LEVELSthere is nothing to quite match the easy perceptibility of pointer instruments. One of the principal reasons forthis is that the meter display moves in an arc while most other things in the operator's field of view are straightlines. Combine this with fast but defined attack, slow fall -back, uncluttered logarithmic scaling and a white pointeron a matt black background and it's a peak programme meter.We produce a standard performance PPM drive circuit which meets BS4297, the proposed revision of BS4297and the proposed new IEC Type 2 meter specifications and fulfils the requirements of the BBC, IBA, EBU andBPO. Reviewed Studio Sound Sept 1976. Under licence from the BBC, based on ME 12/9.Ernest Turner PPM movements 642, 643 and TWIN available from stock.PEAK DEVIATION METERFor monitoring mono or stereo FM stations either off air or at the transmitter. This is a rack mounting unit,calibrated in kHz, percent and decibels, including a 75 kHz deviation standard and a high impedance probe headfor use with a monitor receiver. A 20 dB increased sensitivity switch allows checking of pilot and signallingtonelevels.Observation here shows that many UK and continental FM stations overdeviate at some times and this explainssome of the 'sibilant splashing' complaints familiar to Hi Fi retailers. Monitoring the true peak multiplex devia-tion with a very fast attack -time meter gives much more insight into modulation levels and limiter overshootsthan standard programme meters displaying the decoded and de-emphasised stereo signals. A chart recorderaddition allows continuous records of modulation levels to be made and can show up jumps in level betweendifferent programmes.

SURREY ELECTRONICSTHE FORGE, LUCKS GREEN, CRANLEIGH, SURREY GU6 7BG STD 04866 5997


FIG.4 DISTORTION RANGE SWITCH ERRORS

RANGE%

+

ot .1.

x+

+ C

++

x a

30 I 10 I 3 AI 1 I '3 I +1 I '03

)

I

OMB

x CUMULATIVE ERROR

+ STEP ERROR

correct when measuring total harmonicdistortion.

SummaryWhile this instrument has some shortcomings

it is definitely a very useful instrument when itis required to measure total harmonic distortionof audio equipment and it is one of the fewthat can achieve really good rejection of thefundamental. However, like so many instru-ments of this type the stability of the notchfrequency is none too good.

r r IMPRIIIInvite

YUyou to

StiSTEM

THE PROPESSIONM WAY

dynamic

X enhancersIllit

The DBX 117 and 119 are units*,-', be added to any system to re

dynamic range that has beenthe recording process when

Nilk disc, cassette, open reel andcan also be used to compressvarious purposes includingconstant level background music.

Send for full literature

range

that can-expand thelost duringused withFM. Theysignals forrecording

The DBXimprovementsto 30range(comparedThey alsobe recorded.becomingnoiseDBX

noise reduction

X unitsII models 122 and

in noise reductiondB across the whole frequencywhen used with tape or

with 10 dB forenable a far wider dynamic

DBX encodedavailable possessing

when decoded with thesePROFESSIONAL 150

124

cassetteDolby

recordsa completeunits.SERIES

....: ..

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are now alsoabsence of surface

Send for full literatureALSO AVAILABLE

REW, 230 Tottenham Court Road, London W I. Tel: 01-637 2624/5 Centrepoint, 20-21 St. Giles High Street, London WC2.

Tel: 01-240 3066/7. 146 Charing Cross Road, London WC2. Tel: 01-240 3064/5. Mail orders to: REW House (dept HFN), 10-12 High Street,

Colliers Wood, London SWI9. Tel: 01-5409684/5/6.

AES6sIMMATAPOLLO ELECTRONICS FRANCE

PROFESSIONALaudio plug-in unitsmore than 20 modelsinput channel, amplifequalisers, compressors,expanders, generators,line amplifiers, etc ...

PERFORMANCE AND

RELIABILITY AT A

MODERATE COST ...HYBRID MODULES

24 PINS DIL 33 x 20 x 15mm

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Application data on request/AES PARIS, std B12

22 RUE STE AMBROISE-PARIS 7501I -FRANCE

The Allen and Heath BroadcastFeed Forward Delay Limiter.The only limiter that makes it IMPOSSIBLE for atransient peak to pass through the unit, without the useof clipping devices. Included in its design is arevolutionary bucket brigade integrated circuit. Thisdelays the main signal path by approximately onethousandth of a second. Thus gain reduction is fedforward before there is any increase in the programmelevel. The unit can be used with high powered equipmentsuch as broadcast units and P.A. systems. Use it too instudios with effects units.

Try and test one at our demo. studio. Pembroke House,Campsbourne Road, Hornsey, London N8.Or, for more information, call Andrew Stirling at01-340 3291.

IHAllen and Heath Limited.

57

Amber 4400 multipurpose audio test setHugh Ford

MANUFACTURER'S SPECIFICATIONFunction Generator SectionOutputs: sine,triangle, square, pulse,asymmetrically clipped sine, asymmetrically clippedtriangle.Frequency range: 10 Hz to 150 kHz.Output amplitude stability (20 Hz to 20 kHz):±0.5 dB.Sinewave distortion: 20 Hz to 20 kHz worst case0.1 %, typically less than 0.02% thd.Triangle linearity: better than 1%.Square and pulse rise/fal I time : main output 2µs,pulse output 100 ns.

Sweep Generator SectionSweep: log sweep of sinewave 20 Hz to 20 kHz or100 Hz to 100 kHz.Sweep speed: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512,1024 seconds.Amplitude stability (20 Hz to 20 kHz): ±0.25 dB.

Noise Generator SectionCharacteristics: pseudo random noise.Amplitude accuracy over spectrum: ±0.5 dB.

Comb Generator SectionFrequencies generated: 31.25, 62.5, 125, 250, 500,1k, 2k, 4k, 8k, 16k Hz.Frequency accuracy: better than ±0.01%.Amplitude uniformity: better than ±0.2 dB.Distortion of each frequency: less than 1 % thd.

Output CharacteristicsSource impedance: 50 ohm.Load impedance: 600 ohm nominal, 50 ohm mini-mum.Maximum level: +33 dBm, 600 ohm load.Attenuator: 11 positions, 10 dB per step -70 to+30 dBm.Level control: 20 dB range.Configuration: single ended or balanced.Gating: time or period mode: In time mode, rangeIs approximately 16 ms to 16s. In period mode, range1s 1 to 1024 periods. Switching may be zero crossing.

Receiver SectionModes: wide band sweep for use with swept sine


wave; 20 Hz to 20 kHz tuned log sweep for use withpink noise; manual tune (wave analyser) band pass,band reject, high-pass, low-pass; wideband phaseplot ±180°.Tuning range: 10 Hz to 150 kHz.Amplitude range: -120 dBm to +30 dBm.Memory resolution: 256 x 256 in each of fourmemories.X-axis: 20 Hz to 20 kHz log or 1 to 1024s linear.Y-axis: 10, 20, 30, 40, 50 or 60 dB or ±180°.Tuned sweep speed: 1, 2, 4, 8, 16, 32, 64, 128, 256,512, 1024 seconds.Markers: 10 markers at octave intervals starting at31.25 Hz.Marker accuracy: ±1%.Filter bandwidth: manually adjustable with frontpanel control for approximately 3% to 70%. At 3%,attenuation at IF and 2F better than 30 dB.

Digital DisplayMeasures: level: -120.0 dBm to +30.0 dBm;frequency: 10 to 199 999 Hz.Display: autoranging-reads dBm or Hz.Accuracy: level: ±0.2 dB ±1 digit; frequency: ±1Hz ±1 digit.Resolution : level: 0.1 dB; frequency: 1 Hz.Measurement time: frequency: 1 per second;level: 10 per second.

GeneralPower: 100, 120, 220,240V, +5 % -10 %. Switchable48 Hz to 400 Hz.Dimensions (whd): 178 mm x 406 mm x 305 mm.Weight: 9 kg.Price: £2100; US $2950.Amber Electro Design Ltd, 1064 Chemin du Golf,Montreal, Quebec, Canada.UK agent: Scenic Sounds Equipment, 27/31Bryanston Street, London W1.

T BELIEVE the Amber 4400 multipurpose1 audio test set to be a unique instrument, asit contains within one medium sized cabinetthe functions of at least six conventional

instruments. To start with, there is a sinewaveoscillator covering 10 Hz to 150 kHz; thisoscillator can be swept between 20 Hz and20 kHz or 100 Hz and 100 kHz with a logarith-mic sweep which has 11 switch selected speedsbetween 1 and 1024 seconds.

In addition to the sinewave output, thereare function generator outputs of squarewaveor triangle. It also incorporates a variablemark/space ratio pulse output and the unusualfacility 9f producing an asymmetrically clippedsine or triangle output-very useful foramplifier overload investigations and such.

Clearly some of these functions are unusual;Amber has, unlike so many oscillator manufac-turers, thought about the output requirementsfor testing modern audio equipment and hasprovided a balanced/unbalanced output capableof driving up to +33 dBm-the common +20dBm or so is just not enough these days.Furthermore, the output can be wound downto -80 dBm for use with high sensitivity inputs.

Unusual again-I'm going to keep on usingthat word-there is a facility for superimposingdc on the output at a variable level which willcatch those nasty designs that have dc coupledinputs.

There's much more to come, such as thetone burst facility. This provides tone burstsof either a switched number of cycles between1 and 1024, or of a switched duration between16 ms and 16s. By means of a 2 -positionswitch, the bursts may be arranged to start andstop at a zero crossing or be random inamplitude at the start/stop.

If the above isn't enough, further mentionmust be made of the sinewave sweepingfacilities. This is intended for use in conjunc-tion with an external oscilloscope; the latterdisplays the serialised contents of a set ofinternal digital stores overcoming the shortpersistence of an oscilloscope tube at longsweep times (more about this later). Sweepingmay be continuous at the selected speedbetween 1 and 1024s, or may be single shot atthe set speed. It may sweep up or sweep downand can be manually incremented up or down.An automatic variable speed function called`base line sense' is included. This switchedoption increases the sweep speed when thesignal being examined is below the cursor onthe oscilloscope and reduces the sweep speedwhen the signal amplitude is of interest, thussaving much time when sharp filters are beingexamined.

So far I have not mentioned how the outputlevel is monitored. The instrument contains asingle decimal display which comprises 54digits of 7 -segment display. This display canbe switched to function either as a frequencydisplay when it has a fixed range in integralcycles per second, or it can be switched tofunction as an autoranging voltmeter when itreads in dBm in 0.1 dBm steps between +30dBm and -120 dBm and as a true rms readinginstrument, and with 'fast' and 'slow' averagingtimes.

In the frequency mode the display can showoscillator frequency, input signal frequency orthe tuned frequency of internal filters. In thedBm meter mode the display can read oscillatoroutput, signal input and a number of otherfunctions.

To revert to the remaining oscillator

60

Stones' Rolling. Studio

A complete recording studio in a van? For Mick Jagger, it is almost a neces-sity. Mick and the Stones can be inspired to produce their next hit anytime,but when they're on tour or on vacation, the best recording studios aren'talways around the corner. The Stones rely on their Shure -equipped mobilestudio for the unmatched recording perfection they insist upon, for thesemoments of midnight inspiration. Whether in a recording session or on stage,the Stones' SM7, SM58, SM82, SM53 and SM56 microphones are theirassurance of consistent quality and natural sound.

Shure Electronics LimitedEccleston Road, Maidstone ME15 6AUTelephone: Maidstone (0622) 59881

59

AMBER/4400

functions, in addition to those already men-tioned, there is a fast rise/fall time output atfixed level for rise -time testing. In addition tothe variable frequency sinewave function a10 -frequency comb generator provides crystalcontrolled frequencies on the standard ISOoctave centre frequencies between 31.25 Hzand 16 kHz with the ability to use any combina-tion of these frequencies; and finally there is adigitally derived pink noise output over theaudio spectrum.

And now to the receiving section. I havealready mentioned the ability to measure inputvoltage and frequency with the digital display,but a number of other functions are availablevia the high impedance balanced input. Tostart with, there are four pushbuttons whichselect the metering function which may bewideband (100 kHz), rolled off at 20 kHz orweighted in addition to the fast/slow averagingtime. The 'weighted' function is controlled byan internally pluggable network which can beselected to perform the normal A, B or Cweightings or other filter functions.

In addition to these fixed functions there arevariable frequency and variable Q filters whichmay be switched to bandpass, band reject,high-pass or low-pass with the ability to deter-mine the tuned frequency from the frequencydisplay. To assist with nulling, there is a smallanalogue meter with an associated variable gaincontrol, and also a filter output socket forfeeding further instrumentation.

As an alternative to manual tuning, thebandpass and band reject filters may be auto-matically swept in frequency in the earlier-mentioned 11 steps between 1 and 1024s forsweeps, between either 20 Hz and 20 kHz or100 Hz and 100 kHz with variable Q available.As if this wasn't enough, the final swept facilityis a phase plot which is referenced to a separatephase reference input.

All swept functions which, like the oscillatorsweep, may be manually or automatically sweptcontinuously or incrementally up or down,depend upon an oscilloscope for the display.Many swept measurement instruments requirethe use of a special display oscilloscope, butAmber have completely overcome this require-ment by incorporating a 256 x 256 bit digitalstore, or rather four such stores which may beselected as required. Information is contin-uously entered into the selected store whichmay have its contents continuously regurgitatedto the oscilloscope at high speed to produce aflicker -free display.

Each of the four stores are identical, with a60 dB maximum dynamic range with the facilityof increasing the resolution of the display in10 dB increments down to 10 dB full scale.Naturally only one store can, or need be,entered at any time. However the storedinformation is retained and any single storeor pair of stores can be displayed on theoscilloscope. An added feature is that nooscilloscope calibration is required becausethere is a facility for displaying reference lineson the vertical linear dB axis and also a facilityfor displaying frequency markers on thelogarithmic frequency axis. These markers arederived from the comb generator.

The contents of two stores, when displayedsimultaneously, can be either superimposed fordirect comparison, or may have the displays60 STUDIO SOUND, FEBRUARY 1977

FIG.I AMBER 4400 SINEWAVE OUTPUT LEVEL AT OdB NOMINAL

2dB

=M.

10 20 50 100 200 500 1000

FREQUENCY IN Hz

2K 50 10K 20K 50K

separated by a variable amount complete withseparate reference lines if required.

The complexity of this instrument makes itimpossible to describe all the functions indetail in the space of this review, but it can beappreciated that a large number of controlsare involved to obtain all the functions. Inthis context the front panel layout is a master-piece of ergonomics with the various functionsclearly identified and each functional sectionof the front panel divided into subtly chosencolour shades. Switches are either clearlycalibrated rotary types or the 'self -illuminating'pushbutton types with well chosen colours.However, I do have to complain about the lackof brilliance of the various indicator lampswhich take the form of recessed red ledindicators.

Internally, the instrument is based on threelarge glassfibre printed boards which are ofgood quality and properly identified withcomponent references. I was rather horrifiedto note the proximity of mains voltage conduc-tors to other conductors which are in connec-tion with the chassis.

The main case is of fairly solid constructionand is fitted with a carrying handle/tilting foot.In the latter application (which is definitelynecessary for bench use) the means of securingthe foot was unreliable, with the result thatthe instrument descended on to the bench witha resounding crash from time to time! At therear of the instrument, there is a very neatIEC mains connector cum fuseholder (imperialsize) and mains voltage selector. In additionthere are two multi -pole connectors for usewith ancillary test gear which is said to beunderway from Amber.

Oscillator performanceDealing first with the variable frequency

sinewave function, the flatness of the manualvariable or the swept modes is shown in fig. 1,from which it is apparent that the performanceis considerably better than specification overthe audio band, but that above 30 kHz thereis an undesirable droop in the output to theextent of -3 dB at 100 kHz.

Sinewave distortion was likewise far betterthan specification with the actual harmonicproducts being at an extremely low level, butas is usual with function generator type sine -wave synthesisers, there being a fair amountof 'rubbish' in the output which reflects in themeasurement of total apparent harmonicdistortion.

frequency second third apparentharmonic harmonic total

harmonic125 Hz

1 kHz6.3 kHz

10 kHz20 kHz

0.005% 0.034% 0.045%0.005% 0.008% 0.038%0.005% 0.010% 0.044%0.005% 0.013% 0.052%0.034% 0-045% 0.068%

The accuracy of the indicated frequency waswithin ±1 display digit, ±1 Hz, which is thebest accuracy that can be obtained with theadequate size of display in use.

The output attenuator accuracy was within±0.2 dB up to 100 kHz and even better at1 kHz; but some care is required when interpre-ting the actual output voltage. The arrange-ment is such that output level metering andoutput monitoring to the oscilloscope is locatedbetween attenuator sections, such that the trueoutput is neither being metered (as is commonwith oscillators) or observed on the monitoroscilloscope. The result is that the effects ofloading do not become apparent, and, evenworse, the oscillator is capable of driving itsoutput stage into clipping at +32.5 dBm(+33.5 dBm unloaded?). A further complica-tion of the output metering is that the levelcalibration is nominally arranged to indicatethe output level when loaded into 600 ohms,thus giving a 0.7 dB under reading when thenominal 50 ohm source impedance output isunloaded. Personally I would have preferredthe metering to have been correct whenunloaded, for just how often is one workinginto 600 ohms?

The pink noise output level was found tobe -20 dB rms relative to the sinewave outputwhich gives more than adequate allowance forthe crest factor of the pink noise, and thefrequency spectrum in the audio range wasadequately accurate as shown in fig. 2.

The remaining output waveforms had thesame peak voltage as the sinewave output whenthe waveform was changed, with true rmsmetering. In the case of both the squareand the triangle outputs, the symmetry was,perhaps, not as good as might be expected,this being tied to the measured 1:1.17 mark/space ratio of the square output. Squarewaverise and fall times at the main output dependedslightly on frequency but remained about 3µswith a low frequency tilt of 4 % at 20 Hz whichcould do with improvement. At the separate`pulse' output 4.2V peak -to -peak was available

+6.6 dB -16 dB +6.4 dB -16.9 dB

with a measured rise time of 300 ns and falltime of 500 ns; both are in excess of specifica-tion, but are anyhow quite fast enough foraudio work.

Regarding the comb generator, the frequencyof any selected frequency was within five partsin 105 with amplitude variations betweenindividual frequencies being less than ±0.2 dB;total harmonic distortion consistently aroundthe 1 % mark with the third harmonic pre-dominant. Individual comb frequency outputswere set 10 dB below the normal sine output,such that when all frequencies were selected,the output was virtually the same rms outputas the sinewave output. However, someoneforgot the matter of crest factors ! Select morethan six simultaneous frequencies and some-thing clips at any output level.

The remaining facility which can come underthe heaving of the oscillator is the tone burstfacility which can burst any selected waveformincluding pink noise. While the latter cannotbe bursted for a selected number of cycles(which would be meaningless anyway) it can,like the other waveforms, be started andstopped at zero crossings if desired. Notrouble was found with bursting the fixednumbers of cycles, but a logical error has creptin the burst time mode such that the timecalibrations should be divided by two-thisfor some reason did not apply to sweep timewhich uses the same switch.

Digital voltmeter frequency meterperformance

To take the simplest part first, the frequencymeter was found to be accurate to within fourparts in 105 ±1 digit, a creditable performance.The required input voltage for correct frequencyindication was a worst case of 2.5 mV at 200kHz falling to less than 1 mV within the audiofrequency band for a sinewave input.

The voltmeter section, which reads in dBm,works on a combination of autoranging overa 60 dB range and manual ranging in threeoverlapping 30 dB steps. The autorangingsections of the overall range were within ±0.1dB at 1 kHz, but errors were about 0.3 dB forthe manual step 0 to -60 dBm and 0.5 dB forthe -30 to -90 dBm range. Below -90 dBmthe meter was too affected by noise to beuseful in the wideband mode.

As is shown in fig. 3 the frequency response

was flat up to 10 kHz on all ranges and usefulup to 20 kHz, above which the accuracydepended upon the range selected and becameunreliable.

While the provisional instruction book givesan indication of the useful range of the volt-meter section, I suggest that the manufacturershould give clearer information in the publicitymaterial.

In addition to the unweighted mode, twoweighted frequency responses are available, a20 kHz low-pass weighting and one of thestandard weighting networks which were notin fact fitted to the review instrument. Thevery useful response of the 20 kHz low-passfilter is shown in fig. 4, which demonstrates agood characteristic for rejecting such things astape recorder bias.

Selective measurementsFour filter functions are provided to cope

with high-pass, low-pass, bandpass and bandreject; the latter two functions being capableof being automatically swept in frequency. Allfour functions are tunable from 20 Hz to 100kHz and are also affected by the variable Qcontrol, the effect of this on a fixed frequencybandpass function being shown in fig. 5. It isto be seen that unfortunately the maximum Q

setting reduces the overall gain by 9 dB, whichis, to say the least, an irritating feature. How-ever, at the maximum Q setting the secondharmonic is attenuated by a good 30 dB thusproviding a quite useful wave analyser function,particularly in the swept frequency mode.

A similar situation exists in the band rejectfunction and the effect of the Q control on thehigh-pass function is shown in fig. 6, the low-pass characteristic being a mirror image ofthis plot.

An unusual feature of the selective sectionis that the tuned frequency can be read fromthe frequency meter, and this in conjunctionwith the bandpass mode is a very usefulfacility.

Storage and displayAll that is required in the way of a display

is an oscilloscope with a sweep time of 2 mswhich can be externally triggered, and a verticalsensitivity which can display a 4.5V peak -to -peak signal: the output from the Amber simplybeing two connectors, one for the trigger andthe other the signal.

In fact the only function of the Amber whichcannot be used without a display is the phasemeasurement section, this providing plots of

62

FIG. 3 AMBER 4400 METER

40da

2dB

10 20 50 100 200 500 1000 1K

FREQUENCY IN Hz

50 10K 20K 400

Response error of voltmeter section for nominal readings of +10,-30 and -60 dB:For +10 dB error was +6.4 dB at 50 kHz and -12 dB at 100 kHzFor -30 dBFor -60 dB

(FIG.2 AMBER 4400 CONSTANT BANDWIDTH ANALYSISOF PINK NOISE OUTPUT

3dB OCTAVE

20 50 100 200 500 1000 2K

FREQUENCY IN Hz

50 100 200

61

FIG. 5 EFFECT OF 0 CONTROL ON BANDPASSSHOWING 9dB

DIFFERENCE

BETWEEN

MAX I MIN LI

10dB

MIN 0

MARL

20 50 100 200 500 100 2K

FREQUENCY IN Hz

SK 10K 200

AMBER 4400phase against time or against frequency. Thisfunction was found to be of excellent accuracy,fig. 7 showing the phase vs frequency plot andthe frequency response of a 'B' weighting net-work as a simultaneous display of two stores.

The total of four available stores means thatreference information can be permanentlystored (provided the power remains on) anddirect comparisons made as a result of thecapability of displaying any two storessimultaneously, there being a display offsetfacility for overlaying the two displays.

As is shown in fig. 7, the comb generatorprovides frequency markers as desired and oneof the other beauties of the display is the abilityto select full-scale deflection between 10 dB and60 dB in 10 dB increments, over the input range+30 dBm to -120 dBm. However, it was foundthat the accuracy of measurement was ratherpoor on the more sensitive settings to the extentof 1.2 dB error over full scale.

SummaryThe Amber multipurpose audio test set is

FIG.6 AMBER TEST SET EFFECT OF 0 CONTROLON HIGH PASS FILTER

20 50

10dB

100 200%

500 100FREQUENCY IN Hz

20 50 100 20K 401

FIG. 7 30 dB: 125, 1k, 8k, 20120k.

by far the most versatile piece of audio testgearthat I have met, and at a very low price tag forthe facilities included.

As a result of the complexity of the instru-ment, I have been unable to describe many

featUres and applications in the space of thisreview, and I recommend readers to ask themanufacturer for more information if they areinterested in this type of instrument.

Bearing in mind that this is a new instrument,it is not surprising that I have found a numberof snags, but I am confident that Amber willpay attention to my criticisms. In particular,I would like to see a better defined manufac-turer's specification as, in a few respects, theexisting literature is misleading. Clearly thisis not intentional, but is the result of trying toget a quart into a pint pot.

So far as performance is concerned, theinstrument does not, and is not intended to,compete with the Bruel & Kjaers and GeneralRadios of this world; but, if one considers thecommon testgear in use in maintenance work,the Amber is a good performer at far less costthan the equivalent facilities in the form ofindividual pieces of testgear.

Withreference to this review we are pleased to have receivedfrom Amber the following comments which are generally inagreement with the technical findings of the review. There ishowever a divergence of opinion about some of the opera-tional aspects and it is up to the reader to form his ownopinion.

1. Capability of clipping in power amplifieroutput.The output amplifier clips at just over +33 dBm.This is the specified maximum output and canbe read on the instruments level meter. Anindication, other than the digital readout, wasnot felt necessary as very few tests will involvesuch high levels and good measurement practicewill avoid output clipping.2. dBm level meter requiring a 600 ohm termin-ation on power amplifier output.In fact the meter can be very easily recalibratedto read correctly into bridging loads ifthese aremore often encountered.There are several ways this circuit could havebeen designed. The best would have provided acomplex isolation and gain switched preampacross the actual output terminals and measurethe actual output signal. This would have addedwhat we felt was unwarranted cost. Anotherapproach would have used a lower impedanceoutput attenuator to minimise the effect ofoutput loads. This would have caused largepower dissipation in the power output stage withresulting heat generation, increased distortionetc. The approach we used, that of monitoringthe input to the power amplifier and making the62 STUDIO SOUND, FEBRUARY 1977

assumptions of the output attenuator accuracyand load impedance was felt to be the bestcompromise.3. Oscillator output 3 dB down at 100 kHz.In general the instrument is designed for 20 Hzto 20 kHz range and is provided to give anapproximate 'look' at performance above 20kHz. The design of a particular circuit alwaysinvolves trading performance specifications,cost, features, etc. We felt, for example, thathigh output capability was more important thanresponse beyond 50 kHz, so the power amplifierwas optimised for power output over a 50 kHzbandwidth in place of a lower output capabilityover a larger bandwidth.4. Front panel visibility and cosmetics.The initial panels we received from our supplierhad excessive attenuation of the led lighttransmission. These panels have since beenimproved and steps have been taken to providebetter alignment of the led's with the front panel.5. Carrying handle not sturdy.We feel the locking knobs provided satisfactorilyhold the handle and the instrument in a conven-ient operating position. Again, for added cost alocking mechanism similar to that supplied onoscilloscopes could be provided but the toolingcosts for such a feature are formidable.6. Gate on times one half front panedesignations.We have red faces over this one. A simple logicerror which for some obscure reason went

undetected until this time. Corrective actionhas been taken to modify all units, includingthose already delivered (change is a simple one).7. Comb generator clips when more than sixfrequencies are selected simultaneously.This was carefully checked on a number ofproduction units and not found to be the case.I can only assume that the unit received had adefect-amplitude calibration controls set toohigh or incorrect and excessive gain in thesumming amplifier.8. Square wave duty cycle not exactly 50%.Steps are being taken to correct this. The pulsewave can, of course, be set to exactly 50%.9. Q control affects centre frequency gain.The manual should have stated the Q controldoes not significantly affect passband gain. Theintent was to exemplify the difference betweentwo possible techniques for varying the Q. Onehas constant out of band gain with varyingpassband gain-the skirts remain fixed in thebandpass mode while the peak raises or lowers.The second method, the one employed in the4400, maintains reasonably constant centrefrequency gain but varies the out of band gain-the top of the peak is reasonably constant whilethe skirts move. This latter technique givesvarying energy through the filter but avoidsclipping as the Q is increased. Using the formermethod would necessitate reducing the inputlevel as the Q is increased to avoid overdrivingthe filter or succeeding stages.

This small desk today

...is a big desk tomorrowThe TRIDENT FLEXI MIX portable mixing system provides the comprehensive facilities which would normally be found onlyon an expensivestudio console. This gives Fleximix the big desk 'feel' as soon as you operate it. Add this to the unique expandability of the system andyou can see why it is in a class of its own. For a little over £2000 you can buy a 10 input -2 output configuration, which could sub-sequently be expanded to a system with 10 mixed outputs, any number of input channels and 24 track monitoring. Expansion is simplyachieved by slotting -in additional channel modules. When available slots are used up another mainframe is added. Modules may beplaced in any sequence. No factory rework or rewiring is necessary. Additional mainframes may be either rigidly or flexibly coupledto the original system and flight -cases are available to accommodate any arrangement.

A number of exciting new modules will shortly be available, which will extend even further the system's versatility. These will includea Compressor/Limiter module, Quad Joystick module and Line -balancing module.

If you're looking for a new mixer you've just found it!

Send for details to:

Trident Audio Developments Ltd.,Sales Office: 112/114 Wardour Street,London WI V 3AW.Tel: 01-734 9901. Telex 27782 Tridisc.

Factory address:Shepperton Studios,Squiresbridge Road,Shepperton, Middlesex.Tel: Chertsey (09328) 60241.

TRIAD

United States Agents:East Coast:Audiotechniques Inc.,142 Hamilton Avenue, Stamford, Conn. 06902.Tel: (203) 359 2312.Contact: Adam Howell.

West Coast:Studio Maintenance Service,2444 Wilshire Blvd., Suite 211, Santa Monica,Ca. 90403.Tel: (213) 990 5855.Contact: David Michaels.

63

Brim! and Kjaer Psophometer

MANUFACTURER'S SPECIFICATIONInput: connector; in accordance with DIN 41 628.Construction: symmetrical in accordance withCCITT Recommendation P53. Impedance: 600 ohm

greater than 10k ohm (both symmetrical).Amplifiers: voltage range: 100 µV to 30V fsd in10 dB steps. dB range: -78 dB to +32 dB fsdrelative to 775 mV. Output: 3.16V rms correspondingto fsd (BNC). Output impedance: less than 5 ohmsshort-circuit protected. Gain range: +90 dB to-20 dB. Attenuator: 12 pushbutton combinations,with overload indication of illogical settings. Ear-phone output: 3.16V rms corresponding to fsd, 600ohms.Overload margins: pre -filter overload indicated byflashing led. Pre -filter: at least 30 dB. Pre -telephonefilter: at least 30 dB. +20 dB per decade below1500 Hz (approx 60 dB at 50 Hz). Post -filter: at least20 dB in accordance with CCIR 468-1.Weighting networks: 1) Unweighted in accord-

ance with DIN 45 405.2) Telephone in accordance

with CCITT P53 and DIN45 405.

3) Radio 1 in accordancewith CCITT P53 and DIN45 405.

4) Radio 2 in accordancewith CCIR 468-1.

All filters are solid stateactive circuits.

Noise: equivalent input noise utilising the rmsdetector. 1) Unweighted less than 8µV. 2) Telephoneless than 6µV. 3) Radio 1 less than 10µV. 4) Radio 2less than 14 µV.Detectors: Q-rms detector: in accordance withCCITT P53. Q -peak detector: in accordance withDIN 45 405 and CCIR 468-1. Dc output: 3.16V dccorresponding to fsd (BNC). Impedance: 47 ohmshort circuit protected. Linearity: linearity of bothdetectors re fsd, 0 dB to -10 dB ±0.2 dB, +10 dBto -20 dB ±0.5 dB.Power supply: 100 to 250V ac line 50 Hz to 400 Hzor two 18V to 25V batteries.


Hugh Ford

Temperature range: 5 to 40°CWeight: 3.4 kg approx.Dimensions (hwd): 132.6 x 139.5 x 200 mm.Price (at August 1976): $2100.Manufacturer: Bruel & Kjaer, DK-2850 Naerum,Denmark.UK: B & K Laboratories Ltd, Cross Lances Road,Hounslow, Middx.US: B & K Instruments Inc, 5111 West 164th Street,Cleveland, Ohio 44142.

WHAT on earth is a PSOPHOMETER?You may well ask. Well, it doesn't

appear in my dictionary but is pronouncedsomething like pissometer and it's used tomeasure noise . . . in communications systems.

Actually, the Bruel & Kjaer 2429 psopho-meter is a multi -range voltmeter equipped withnoise weighting networks and rectifier charac-teristics fulfilling the requirements for noisemeasurement to the latest standards in audioequipment in the broadest context.

Until fairly recently there have been veryfew instruments which have been capable ofmeasuring noise to the CCIR weightingcharacteristic which has been shown to give afar better correlation with the subjective effectsof noise than earlier weighting curves. Further-more, meters which comply with the DINquasi -peak rectifier characteristic and the DINstandard 45 405 for ballistic performance have,I believe, been restricted to one manufacturerwho has sold the instruments under more thanone trade name.

In the interests of international standardisa-tion, Bruel & Kjaer have taken this horriblemuddle to task and produced an instrumentwhich is up to date in conception and providesboth the necessary weighting curves and the

standard rectifier characteristics, but at a pricewhich, in terms of the £ sterling, is astro-nomical. However, having recently visitedDenmark, I have learnt that if you divide thecost of things by two to allow for the Danishcost of living, the prices become realistic. Sincethere is no alternative instrument yet available,you have to pay the cost if you need to makethese measurements of noise.

While there are alternative instrumentsavaitable with the CCIR 468-1 weighting curve,none of these have the quasi -peak readingmeter which is demanded by CCIR 468-1 andwhich is identical to the DIN requirement asper DIN 45 405.

The Psophometer also offers a floating inputwhich may either be a fairly high impedanceor be terminated into 600 ohms. A rear panelfacility for listening to the weighted noise onheadphones in included.

The form of construction is the now familiarB & K Cassette modular system with a clearlyscaled and illuminated front panel meter com-plete with anti -parallax mirror. Meter scalingcomprises a dB scale ref 0.775V from +2 dB to-20 dB and two voltage scales covering 0 to 10and 0 to 3. These scales operate in conjunctionwith two pushbutton attenuators, one is a 60 dBstep providing volts or millivolts scaling; thesecond consists of six interlocked pushbuttonswhich provide 10 dB steps thus providing full-scale sensitivities between 100 vN and 30V(-80 dB to +30 dB ref 0.775V).

The desired frequency response weighting isselected by four further interlocked push-buttons which allow an unweighted functionor any of three weightings which are 1) Tele-phone weighting to CCITT P53, 2) radio 1weighting to DIN 45 405 and CCITT P53, and3) radio 2 weighting to the recent CCIR pro-posal 468-1. From the audio equipment user'spoint of view, the latter is the most valuablecurve. For the cost of this instrument, it isunfortunate that the common 'A' weightinghas not been included. Furthermore, as willbe seen the unweighted condition does notfollow the recommendations of CCIR 468-1for unweighted measurements, but complieswith the requirements of DIN 45 405 unweigh-ted standards which, so far as I am aware, arelittle used.

I have discussed the problems of otherweighting networks and alternative `unweigh-ted' frequency responses with Bruel & Kjaer,and I am informed that the instrument will beavailable with a number of alternatives whichwill be achieved by changing the internalprinted circuit boards to alternative types.

Overload of the pre -weighted or post -weighted signal electronics is indicated by ared led on the front panel. This unusual featureis a valuable asset since it is easy to obtainfalse noise measurements in most meters whichrun into peak clipping; these may not givesignificant meter deflections if high crestfactors are involved.

Input to the meter is via three sockets whichaccept standard 4 mm banana plugs or aspecial three -pin plug to DIN 41 628 which isprobably almost unknown outside Germany!One input pin is signal ground within theelectronics, while the remaining two pins arethe floating input selectable to 600 ohms orhigh impedance by means of a front panel slide

66

ROLANDOLAND SYNTHESIZERSYSTEM 700

3

1

The complete system consists of the MAINCONSOLE, the KEYBOARD CONTROL-LER, and five optional blocks for a total of47 modules.

MAIN CONSOLE:The MAIN CONSOLE contains all the basicmodules necessary in a professional systemfor the synthesizing of sound and can beused alone with the KEYBOARD CON-TROLLER as a complete synthesizer initself. Modules included are: VCO (3),VCF (2), VCA (21, LEO (2), S/H, ADSR(2 x 1), OUTPUT MODULE (which includesPANNING controls, REVERBERATION,and a PHASE SHIFTER), and others.

KEYBOARD CONTROLLER:The 61 key (5 octave) two voice KEY-BOARD CONTROLLER has PORTA-MENTO and PITCH BEND controls.

OPTIONS:Optional blocks can be chosen and arrangedaccording to the particular needs of eachstudio. All of the modules in the optional

blocks are interchangeable, thus thenumbers and types of modules can also bechanged to suit the studio. The mainmodules of the optional blocks are: BLOCK3 ..Sequencer: 3 channel, 12 step se-quencer; BLOCK 4 <VCO bank: VCO(61, ADSR (2 x 1); BLOCK 5 VCF/VCAbank -: VCF (2), VCA (3), ADSR (2 x 2).;BLOCK 6 <Interface/Mixer>: frequency -to -voltage converter interface, 9 channelaudio mixer, fixed filter bank, VCA; BLOCK7 <Phase Shifter/ Audio Delay 2 channelphase shifter, 2 channel audio delay.MAIN FEATURES:All modules are made from high qualityparts to ensure high reliability and durabilitywith circuit designs which give high stabilityfor ease in recording perfect sounds.All major modules contain both audiosignal input and control voltage inputmixers for better signal to noise ratiosand ease in synthesizing sounds.Input and outputs are designed for matchingwith other professional audio equipment for

ease of use in the studio.On the MAIN CONSOLE, most commonconnections are made internally without theuse of patch cords. All modules have pro-visions for external patch cord connectionsfor greater freedom in patching.External sound sources (such as othermusical instruments) can be used as a sourceof control.The PULSE SHAPER and the sequencer'sMASTER CONTROLLER input and outputjacks allow the recording of consecutivesequences on tape without a break inrhythm.Except for the MAIN CONSOLE, allmodules are completely interchangeable andcan be arranged to suit individual tastes.(The MAIN CONSOLE can be specialordered direct from the factory in otherarrangements).A complete system, the System 700 containsall the elements necessary for the synthesisof sound.

11=2Roland

Roland's 'System' Synthesizer Series are specifically engineered for professionalrecording studios. The top -of -the -line 700 provides full control over allsynthesizer functions, extremely stable output and a frequency range from0.1 to 100kHz. And this revolutionary new product is one of the most competitivelypriced, full -feature units on the market today.

Brodr Jorgensen (U K) Ltd., Unit 6, Great West Trading Estate,Great West Road, Brentford, Middx. Phone. 01-568 4578.

114J

U

65

BRUEL & KJAERPSOPHOMETERswitch. The final front panel facilities consistof a pair of slide switches, one of which selectsthe rectifier characteristic to be quasi -peak ofquasi-rms and the other of which injects afixed level 1 kHz tone for meter calibration.

At the rear of the instrument there is theIEC mains connector and a voltage selector/fuse holder which are properly identified andprovide for all the common mains voltages.There are next two banana sockets/terminalswhich may be linked to connect the signalground to the chassis or may be used otherwiseto avoid ground loops. While these are onstandard 19 mm spacing, two similar connec-tors for headphone monitoring are annoyinglyon non-standard spacing. Two BNC socketsprovide an ac output at 3.16V rms correspond-ing to full-scale meter deflection and 3.16V dcon a linear scale. Finally there is a 7 -pinDIN socket which duplicates these two outputsand also provides for dc powering of theinstrument from ±18 to +25V sources inaddition to allowing variation of the metertime constant by means of an externalcapacitor.

Like the DIN sockets found in other recentB & K equipment, this is of the cheap andnasty non -locking type-I really do think that

the use of such domestic quality connectorson this class of equipment is absurd.

The internal construction of the instrumentis another story with the best quality printedboards, six of which plug into a mother boardby means of gold plated pin -type connectors.Only good quality commercial components areused and, as is to be anticipated, the standardswithin the instrument are first class.

PerformanceThe frequency response from the input to

the ac output (which is identical to the meterindication) is shown in fig. 1 in the unweightedcondition. It shows that the high frequencyresponse has been rolled off very rapidly withthe -3 dB point at 24.5 kHz and that the lowfrequency end has been cut. This responsemeets the DIN unweighted standard which isdifferent from the more important CCIR 468document.

Close examination of the CCIR and theDIN weighting networks-the broad character-istics of which are shown in fig. 2-showedthat the instrument followed precisely the DINcurve with negligible discrepancies. In the caseof the CCIR curve the mid to low frequencyperformance was also precise but in the earlyreview sample a known error existed in thevery rapid high frequency roll off. In theunweighted mode the overall response was not

FIG.I B&K 2429 UN WEIGHTED FREQUENCY REPONSE

f10dB

5 10 20 50 100 200 500 1000FREQUENCY IN Hz

2K 5K 100 20K 5 K

FIG.2 B&K 2429 WEGHTING NETWORKS

10dB

TELE HONE

CCIR

DIN

20 so 100 200 503 1000FREQUENCY N Hz

2K 5K 10K 200


particularly flat and in my opinion ratherdisappointing with the following toleranceswith respect to 1 kHz which are within the DINunweighted tolerances: 30 Hz -0.4 dB, 37 Hz-0.2 dB, 1 kHz 0 dB, 10.3 kHz +0.2 dB, 16.8kHz +0.4 dB, 20.7 kHz 0 dB.

It was pleasing to note that the frequencyresponse was not affected by the attenuatorsand that, while the 60 dB attenuator was veryaccurate, it was again unfortunate that onestep it the 10 dB selector introduced an errorin excess of 0.2 dB which is excessive for thisclass of instrument. The attenuator errors interms of step error and cumulative error areshown in fig. 3, illustrating this criticism. Thisdefect will, I am assured, be corrected in laterproduction.

In contrast the scaling error and readabilitycombined as shown in fig. 4 was minimal andthe scale calibrations were well chosen formaximum resolution. The absolute accuracyof the instrument is checked by means of a1 kHz internal reference oscillator arrangedsuch that half scale should be indicated withall weighting networks. When the instrumentwas warm this level check was found to be1.4% too low, the situation being reasonablewhen warm but the -2.4 % error when cold ison the excessive side. Again I am told thatthis defect is peculiar to the pre -productionbatch. 68 0.

FIG.3 ATTENUATOR ERROR REF 30V RANGE

RANGE (VOLTS) 60dB STEP

10 ,'--. , .,

3

+ K

- -4 K

I+

4-K K

K

01d0

x CUMULATIVE ERROR

+ STEP ERROR

cmr.IV 4FIG SCALE ERROR IN 2dB STEPS REF ES

B4-6

K

-10

+

-12 -14 dB

4. K.1.

K Kot

K

+

61dB K

X CUMULATIVE ERROR

STEP ERROR

The Amcron Story1967 1977

In 1967 Amcron (Crown International) introduced the world's first 'Super -Amp'. This was theDC300! It rapidly became a must for all the major recording studios and top bands such as Zeppelin,Jethro Tull and the Moody Blues.

The DC300 set new standards of sound reproduction never previously available for bands or studios,let alone the Audiophile (whoever he is). Coupled with the incredibly rugged construction, andsmall size of this 600 watts amplifier, it is not surprising that the DC300 became a legend in its time.The designer of this classic is still in charge of the design work at AMCRON despite rumours that hehas moved on to at least five other establishments! Indeed, he has since been responsible for theDC300A, the DI50A and all the rest of the AMCRON range of superb power amplifiers.Now in 1977, the DC300A is 'the' amplifier in all the world's recording studios and is still the onlychoice for bands such as Zeppelin, Jethro Tull and the Moody Blues, plus quite a few others such asWings, the Stones, the Rollers, Elton John, 10c.c., Pink Floyd, Barclay James Harvest, The Real Thingand so on ,

Perhaps this is because the DC300A amplifier offers the following features:

* Total Harmonic distortion at full power, I Hz-20kHz below 0.05%

* I M distortion 0.01 watt to 150 watts into 8 ohms below 0.05%

* Hum and Noise better than 110db below 150 watts

* Power Bandwidth I db, -0 db from DC to 20kHz at 150 watts into 8 ohms

* Full 3 year warranty on parts and labour

* Patented Crown Protection Circuitry requires no circuit breakers or relays

* Designed to operate into load impedances as low as I ohm

* Manufactured by a company founded in 1946 and represented by the MACINNES peoplecontinuously for the last ten years!

MACINNES LABORATORIES LTD.MACINNES HOUSE, CARLTON PARK INDUSTRIAL ESTATE,SAXMUNDHAM, SUFFOLK IP17 2NL TEL: (0728) 2262 2615

MACINNES FRANCE S.A.R.L.45 RUE FESSART,PARIS 19eTel. 203.30.01

67

BRUEL & KJAERPSOPHOMETER

Precise checking of the overload points inthe instrument were difficult without delvinginto the circuit, but a fairly general checkshowed that the input end had at least 40 dBmargin for normal conditions and the postfilter section in excess of 20 dB-no cause forcomplaint here.

Similarly the inherent noise was found tobe well below the specifications, but care hadto be exercised with the ac output from thepoints of view of headroom and of noise; thesame applies to the headphone output whichappeared to be in parallel. Firstly, the nominalrms output of 3.16V corresponding to full-scaledeflection was accurate, but the margin abovethis level at the onset of output clipping was10 dB which meant that the output could clipbelow full-scale deflection and without indica-ted overload conditions. Secondly, theminimum dynamic range did not correspondto maximum instrument gain as would normallybe anticipated but occurred at relatively highinput signal levels. The result was that boththe ac output and the headphone output hadminimum dynamic range under unexpectedattenuator settings which meant that the 20 Hzto 20 kHz noise was only 50 dB below 3.16Vrms corresponding to full-scale deflection. In

some circumstances, these matters could createa limitation.

Output impedance at the ac output wasextremely low and that at the headphoneoutput was 560 ohms, which provided anadequate impedance and level for many typesof headphone without interaction with the acoutput. Furthermore neither output interactedwith the meter indications.

The dc output which also gave 3.16V forfull-scale deflection (with a ceiling of 14V) wasproportional to meter deflection and was foundto be accurate to better than 0.1 dB down to-20 dB meter indication and to have a satisfac-tory output impedance of 44.7 ohms.

Checking the quasi -peak meter characteris-tics showed that the effective ballistics compliedprecisely with the nominal centreline of theCCIR and the DIN standards and the metercalibration was such that switching betweenquasi -peak and rms detection did not alter themeter deflections, as is correct.

So far as the rms rectifier is concerned, thisis a true rms rectifier but the effective meterballistics are not to the commonly used 'fast'international standard. The effective ballisticsare in fact designed to meet the requirementsof CCITT P53 to the test method suggested bythe UK Post Office. This has resulted in aninstrument which overshoots by 0.8 dB when acontinuous level is suddenly applied, the ,,0 to

-20 dB fall and rise times being 360 ms and190 ms respectively.

SummaryThe B & K 2429 psophometer is an instru-

ment which fills a long-standing gap in noisemeasurement; however, it will also make a verylarge gap in your bank balance. So far as itsconcept is concerned, the instrument is ratherrestricted to fill this specialised gap in theCCIR noise weighting and quasi -peak standardmeter field, in addition to the CCITT telephoneweighting problem.

Unfortunately, with the exception of 'homemade' instruments there is a distinct lack ofsuitable instrumentation to meet these estab-lished standards. If you tot -up the real costsof 'home made' instruments, the 2429 couldbe a reasonable investment and it must beremembered that Bruel & Kjaer represent aninternational standard as a result of the world-wide use of their measuring equipment.

Bearing in mind that the review sample wasone of the first production batch of 'demonstra-tion' instruments, one may be able to forgivethe shortcomings found in this sample, but inmy experience of Bruel & Kjaer, while thedetailed matters may be a sample defect, theoverall concept of this instrument is restrictedto a limited range of specialised measurementsand it will take time to change them.

CRAIGHALL STUDIO

NEW NEVE 805824/16 SOUND CONSOLETHE FIRST TO BE INSTALLEDIN U.K. STUDIO

FULL 2, 8 AND 16 TRACKFACILITIES

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RECONSTRUCTED CONTROL ROOMENLARGED STUDIO CAPACITY

rr. 118 Mil .

mmm .

CRAIGHALL STUDIO, 68 CRAIGHALL ROAD, EDINBURGHTEL. 031-552 3685


S.500D Specification Features* Power output 340W R.M.S. into 4 ohms

500W R.M.S. into 2.5 ohms* Bridged Mono output 900W R.M.S. into 5 ohms

640W R.M.S. into 8 ohms* Intermodulation Distortion Less than 0.02% from

20Hz to 20KHz Fl 60Hz.* Integral "Force Cooled Dissipators" for reliable

operation into adverse loads.* Power Bandwidth +0, -1dB from D.C. to 20KHz.* Very low Transient Intermodulation Distortion.

Restricted rise time, fast slew rate.* Input sensitivity 0.75V for 300W into 4 ohms.* Noise 105dB Below 180W into 8 ohms 10Hz to

20KHz. Unweighted.* Elaborate system protection against short and

open circuit operation* Small size 31/2" x 19" Rack mounting.* 1KVA Toroidal power supply providing 55 joules

of energy.

The S500 -DA higher standard of poweramplifier designFrom the most experienced, well equipped specialist manufacturerof 'Professional Power Amplifiers' in the U.K.

VIKING WAY, BAR HILLCAMBRIDGE CB3 8ELTEL: CRAFTS HILL (0954) 81140TELEX: 817515 HH ELEC GPROFESSIONALAUDIOELECTRONICS

HRHelectronic

IF YOU USE SPOT AUDIO INSERTS, WE COULD HELP YOUThe NAB cartridge system was developed primarily for broadcast applications, and Amity ShroederCartmaster machines are in daily use producing jingles and commercials for just this. However, unlike their

imported competitors, their price puts themwithin reach of many other users relying so faron hand -cued, open reel machines (theatricalsound effects, lectures, educational systems,repeated messages in public places, enter-tainment complexes etc).The Cartmaster is designed and built to profes-sional standards in Great Britain. It uses stockcomponents throughout, a very heavy dutyPAPST motor for ultimate reliability, all plug-in board construction for ease of maintenanceand all machines include as standard the veryuseful automatic fast forward facility.If you use the cartridge system and need toexpand your equipment or if you need spotaudio inserts of high quality call AmityShroeder on the number below. We'll be gladto arrange a demonstration.

As supplied to BBC tv training, John Wood Studios, LeewardSound, CTVC, and others.

AMITY SHROEDER 3-4 NEW COMPTON STREET, LONDON WC2.PHONE 240-3159 or 836-7811. TELEX 23197

(AMITY SHROEDER IS PART OF THE ORANGE MUSICAL INDUSTRIES GROUP OF COMPANIES)

When only the best will do

Undoubtedly the world's finestselection of audio equipment.The range includes poweramplifiers from 50 to 400 wattsper channel, pre -amplifiers anddigital tuners. All units fullyguaranteed for 5 years. Forthe most discriminating en-thusiasts only.Main West End Agents:

RE REW Centrepoint,20-21 St Giles High Street,London WC2. Tel:01-2403066 7 230 Tottenham Court Road,London WI. Tel: 01-637 2624 5

TRADE ENQUIRIES: D.E.S. Technical Co., 10-12 High St.,Colliers Wood, London SWI9. Tel: 01-540 8944.


London College of Furniture41-71 Commercial Road, London El 1 LA.

Two SeniorLecturers

are required to take responsibility for a range of activities in THEDEPARTMENT OF MUSICAL INSTRUMENT TECHNOLOGY. Assist the Head of the Department in its general management andto act as Course Director to the 3 -Year Full -Time Course.

Take responsibility for the large Piano Section.

The Department's areas of specialist study include the design andconstruction of: Pianos, Violins, Fretted Instruments, Woodwind,Harpsichords, Electronics for Musical Instrument Technology.

Candidates should have had significant experience either as amusical instrument maker or management level in a related industryand appropriate experience in the field of education.Salary Scale: £5,031-£5,955 ((bar) £6,417) plus £312 supplementand £402 Inner London Allowance.

ileaSend s.a.e. for details and application form tothe Senior Administrative Officer at the CollegeClosing date -14 days from the appearanceof this advertisement.

Classified AdvertisementsAdvertisements for this section must be pre -paid. The rate is 14p per word, minimum £2.80. Box Nos. 35pextra. Semi -display rates on application. Copy and remittance for advertisements in March 1977issue must reach these offices by 20th January 1977 addressed to: The Advertisement Manager,Studio Sound, Link House, Dingwall Avenue, Croydon CR9 2TA.Note: Advertisement copy must be clearly printed in block capitals or typewritten.Replies to Box Nos. should be addressed to the Advertisement Manager, Studio Sound, Link House, DingwallAvenue, Croydon CR9 2TA, and the Box No. quoted on the outside of the envelope. The district after BoxNo. indicates its locality. SEX DISCRIMINATION ACT 1975: No job advertisement which indicates orcan reasonably be understood as indicating an intention to discriminate on grounds of sex (e.g. by invitingapplications only from males or only from females) may be accepted, unless (1) the job is for the purpose ofa private householder or (2) it is in a business employing less than six persons or (3) it is otherwise exceptedfrom the requirements of the Sex Discrimination Act. A statement must be made at the time the advertise-ment is placed saying which of the exceptions in the Act is considered to apply.

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5". 534: 7"" in bulk

Plasro Plastics Ltd.38 Wates Way, Mitcham, Surrey, CR9 4HRTelephone:01-640 0145/9

*J & B Recordings. Tape to disc. 12in. L.P.£4. 7in. 45 r.p.m. £1.80. E.P. £2. Pressings-stereo/mono. Tape copying. 14 WillowsAvenue, Morden, Surrey. 01-648 9952. X*Your Tapes to Disc, Mono or Stereo cutting.Vinylite pressings, Sleeves/Labels. Top profes-sional quality. S.A.E. for photo leaflet.Deroy Records, "Eastwood", Cove, Dun-bartonshire, Scotland. X*Sound News Productions. Britain's oldestfull-time tape/disc cassette transfer service.Direct transfers, pressings for private and forthe trade. Fund-raising advisory service forSocieties, Choirs, Bands, Ferrograph, Grundig,Philips, Revox equipment promptly serviced.18 Blenheim Road, London W.4. Tel. 9951661.

ALSO A SUPERB 8TRACK RECORDING STUDIO

SPEECHMUSIC

SUN RECORDING SERVICES LTD. STEREOMONO

Tel: 0734-59564734-36 Crown Street, Reading, Berks.

SPEECH -PLUS RECORDINGS LTDSpecialists in Recording for

Education, Commerce, Industry.A/V Programmes/Pulsing for Training and Sales.

Cassette and Open -reel Duplicating

32 PAGES WALK, LONDON SEITelephone: 01-231 0961/2

FOR SALE -TRADE

TRAD: CARDINGTON 404 All Studio Equipment bought and sold.

See our advertisement on page 39.

Dog House, Cople, Bedfordshire

*16/8 RAC mixer, as new,usual facilities,£800.New 101 NAB spools, £1 each. Leader tape,etc. Tel. Copthorne 712550.

*Four Spendor BC111 speakers, teak cabinetand suspension units, £320 per pair plus VAT.Three Westrex Acoustilens loudspeakers, £550for two, £750 for three, plus VAT. TwoCentury Stereo Amplifiers, 100 watts perchannel, £200 each plus VAT. Tel. No. 021-356 9636.*Studer A80 8 track tape machine, lin., excel-lent condition. Impulse Studio, 71 High StreetEast, Wallsend NE28 7RJ, Tyne and Wear.Tel. (0632) 624999.*Revox A 7,00's and a selection of spares andaccessories from stock. Net professional priceson application. We also offer a prompt andcompetent hospital and conversion servicethrough our Reading office. Call: Chymes ofReading on 0734-690177 (24 hours).

SOWTER TYPE 3678MULTITAP MICROPHONE TRANSFORMERPrimary windings for 600 ohm, 200 ohm and 60 ohmwith Secondary loadings ,from 2K ohm to 10K ohm.Frequency response plus/minus }dB 20 Hz to 25 kHz.Contained in well finished Mumetal box. 33mm dia-meter by 22mm high, with colour coded end leads, lowdistortion. DELIVERY (small quantities) EX STOCK.HIGHLY COMPETITIVE PRICE. FULL DETAILS ON

REQUESTE. A. SOWTER LTD, Dedham Place, Ipswich,IP4 IiP Telephone 0473 52794

THE UHER PEOPLE OFFERS/H UHER 4000S single speed ...S/H UHER 40005 4 -speedS/H UHER 4000LS/H UHER PILOTONES/H UHER Converted PILOT XTALS/H PHILIPS EL 3503 CONSOLE

£89£I15£149£450£345£325

All S/H machines guaranteed overhauled tomakers' new specifications.UHER CR 124 STEREO CASSETTE £149UHER 4000 IC ... £245UHER 4200 IC STEREO £275The above are new but shop soiled.4000S UHERS CONVERTED TO 4000Lspecs, with genuine factory parts. £59 plusVAT and carriage.

UHERS SERVICED BY UHER-TRAINEDENGINEER

MICROPHONESLATEST Sennheiser 802 Electret Gun

Mike ... ...L84-60Wind Gag f8.50

S/H MIKESAUDIO RM7 Radio Mic £175NEUMANN KM54 Cardioid... £95AKG D109 ... E19AKG D24 and gag ... E39AKG D25 in mount ... E35ELECTROVOICE 649B Lavalier .. E16ELECTROVOICE GUN MIC E95BEYER M119 Reporters Mic £15STC 4105A CARDIOID E39STC 4038 STICK ... £36NAGRA 3 -WAY MIXER ... E175

VAT and carriage extra on all items.

PAUL SIMMON LTD.2 Market Street, Halifax, West Yorks

Tel. 0422 52240/57442

Open 9-5.30 Mon. to Sat. Thurs half -dayclosing.

71

FOR SALE - TRADE(Continued)

AN EDITING REVOX

Easier threading

Easier editing

Easier head cleaning

Reel switching option

Tape mute option

End of tape lamp switch

The 'OPEN PLAN' conversion makesthe Revox A77 more versatile,convenient and quicker to use.

New machines supplied alreadyconverted

Existing machines convertedConversion kits available

K. L. SOUND23 REDAN PLACE,LONDON W2 4SA

Tel: 01-229 0102

[We've got it taped!Open reel and mono/stereo

cassette duplication at competitive pricessmall or large runs.

Printing of cassette labels and insert cardspresents no problems - ask for a quotation!

Sound Communication (Publishers) Limited,Dewsbury, West Yorkshire. Telephone (0924) 469436

ALLINGTON AUDIO DEVELOPMENTS

794 (A2) Mansfield Road,

Nottingham. Tel. (0602) 624910 3Ct

0(13

3',CASSETTE FAST COPYING

MONO/STEREOOne off or on -going work.

From 15p (+VAT) per copy. Details from:GOSPEL CASSETTES (SS)67 Ashfield Drive, Halifax,West Yorkshire H X3 5PQ.

Tel: Halifax (0422) 59403

r

r

OWN A MINI NAGRA SN ?Then realise its full potentialfor the first time with the

DOCUMENT SQN CONTROL UNIT

Illustrated brochure available fromsole manufacturer:-

DOCUMENT GROUP LONDON Ltd.THIRD FLOOR, 8-12, BROADWICK ST.,LONDON, W1V 1FH.Telephone: 01-437 4526/7.Cables. F ILMDOC LONDON VV1 England.

BROADCASTCARTRIDGE MACHINES

for sale orlong/shortterm hire. Record/playback and playback only from stock.Audiopak's also available.

Tel: Herongate (027787) 531


*Cathedral Sound manufacture a very usefulcompressor for less than £25, and a range ofinput and mixer modules from £12.50. A stampwill bring details by return. Cathedral Sound,Fourways, Morris Lane, Halsall, Lancs L398SX. Telephone Halsall (0704) 840328. X*Disc -cutting styli for all types of mono andstereo disc - cutting heads. Heater windingsfitted, relapping and specials. County Record-ing Service, London Road, Binfield, Bracknell,Berks. Tel. Bracknell 54935. X*Scotch 207 and Maxell professional record-ing tapes on 1011in metal reels. Lowest prices.The Music Laboratory. Tel. 01-346 4469. B

SALECONTENTS OF 16 TRACK STUDIOincluding: Tape recorders, Mixing con-soles, Microphones, Reverberation de-vices, Dolbys, Compressor / Limiters,Delay units, Grand piano, Microphone

stands, etc.

Viewing by appointment with MalcolmJackson, The Studios, Rickmansworth,

Herts, EnglandTel. Rickmansworth 09237-72351

Telex 262284 Ambsdr G

10 OUTLETDISTRIBUTION AMPLIFIER 2

One floating input, 10 floating outputs at 600 ohms forgeneral studio work, feeding multiple slave pa amplifiers ordriving foldback headphones. Electronic input circuit whichwithstands mains or static voltages on the signal lines.DISTORTION, all outputs loaded, at I2dBV.7.

1KHz 0.005%30Hz -20KHz 0.05%INTERMODULATION DISTORTION 50Hz + 7KHz, 4:1

Output -i- I2dBV.7. 0.005%The unit meets the IBA 'signal path' specifications and is

available as a complete unit or as a set of all parts excludingthe case and XLR connectors.

STEREO DISC AMPLIFIER 2SUPERLATIVE PERFORMANCE FOR BROADCASTING,DISC MONITORING AND TRANSFER. Magnetic cartridgeto balanced lines with HF and LF filtering. Mains powered.Meets IBA specification.

SURREY ELECTRONICSThe Forge, Lucks Green, Cranleigh, Surrey G U6 7BG

Telephone STD 04866 5997

RAC MIXERSRAC custom built mixers for studios, hospital radio.discos, etc.

RAC Audio modules: MA 3.1 BAL. MIC. AMP E13.79MA 2.7 MIXER E5.46MA 2.1 OUTPUT AMP E5.70

etc.RAC 100W AMP E77.27, case E19.44All prices include VAT at 8% and connectors withmodules.

RUGBY AUTOMATION CONSULTANTS19 Freemantle Road, Rugby

Tel. 0788-810877

SOWTER TRANSFORMERSFOR SOUND RECORDING AND REPRODUCING EQUIPMENTWe are suppliers to many well-known companies,studios and broadcasting authorities and were estab-lished in 1941. Early deliveries. Competitive prices.Large or small quantities. Let us quote.

E. A. SOWTER LTD.Transformer Manufacturers and Designers

7 Dedham Place, Fore Street, Ipswich 1P4 IJPTelephone 0473 52794

SERVICES*R. Beaumont, specialist audio repairs andPhilips VCR service, 21 Southway, Ilkley,West Yorkshire. Tel. 094-33 2026. X*Tape Copying Service. Open reel and cassetteavailable. The Music Laboratory. 01-346 4469.

B

REVOXSERVICE CENTRE

* Service and overhaul.* High speed conversions.* Head changes.* Self sync.* Automatic Double Tracking.* Varispeed/varipitch.

01-346 4469

STUDIO EQUIPMENT SERVICES

Supply Uher 4000IC, 42001C,SG560 (Stereo, Audio and Pulsetrack for A.V. work), and access-ories with rapid service facilities.

We have a quantity of soiledbut new 40001 C, 42001 C.

01-200 1229

WOLLENSAK 2770AVCASSETTE FAST -COPIERSCS Appointed Main Dealers

Demonstrations Personal Service MaintenanceCassette Fast-Copying-Short or Long Runs

Telephone enquiries welcome

SOUND CASSETTE SERVICEPO Box 2, Gerrards Cross, Bucks SL9 8EG

Tel: 02813 84409

FOR HIREREVOX A77 (HS+standardNAB--CCIR vari-pitch,vari-speed etc.). AKG BX20,QUAD 303, REVOX A78,SPENDOR and GALE speak-ers, mic stands. AKG mikesetc.

Radio RecordingsTelephone: 01-586 0064

High speed cassette copying andMastering Service.

We specialise in small quantities as wellas long runs.

MORARD SOUND PRODUCTIONSTHORNTON HEATH, SURREY

TELEPHONE 01-689 7424.

WANTED*All Nagra equipment urgently required forcash. J. J Francis (W.G.) Ltd., ManwoodHouse, Matching Green, Harlow; Essex CM17ORS. Tel. Matching 476. X*Christian Charity urgently requires timingmechanism for their Revox A77. P.O. Box 11,Tunbridge Wells TN2 5ED.

*Sound Techniques System, 12 input modules,also group output modules. Impulse Studio,71 High Street East, Wallsend NE28 7RJ.Tyne and Wear. Tel. (0632) 624999.

STUDIO EQUIPMENT SERVICES WANTED URGENTLY

I -4T finch Tape Machine.2-8T I inch Tape Machine.Ampex, 3Ms or Studer.IAN DOWNS 01-200 1229

SITUATIONS VACANT

METRORADIO

Require anAUDIO ENGINEER

Grade ILRI or ILR2. Preferablywith Broadcasting experience.

For further details apply in writing to

Mr. Neil RobinsonMetro Radio, Newcastle,

NE99 IBB

Senior Development EngineerAudio Circuit Design

Pye TVT is a highly successful company in the International field of broadcastengineering. We wish to appoint an experienced development engineerfor a senior position in our audio department.The duties involve design and development of a wide variety of audio productstogether with some supervisory responsibilities. We would prefer a background ofexperience in audio engineering or related fields, but proven circuit designcapability including the application of digitaltechniques is the main criteria. Youshould be 25-40 and qualified toB.Sc. or HND/HNC standard.The successful applicant willbe offered an attractive salaryand, if applicable, generousrelocation assistance to thispleasant part of East Anglia.Company benefits include goodcatering facilities, staff shop,pension fund and an activesports and social club.

Apply to Mr. David Barnicoat,Pye TVT Limited,P.O. Box 41, Coldhams Lane, Cambridge CB1 3JU.Tel. Cambridge (0223) 45115

Pye TVT LimitedThe Broadcast Company of Philips

73

UNIVERSITY OF DURHAM

ELECTRONICS TECHNICIAN FOR THEDEPARTMENT OF MUSIC

Applications are invited from suitably qualified Electronics Techniciansfor the above post, starting March,'April 1977. Duties will include servic-ing and maintenance of the existing analogue electronic music system;candidates should have an aptitude and enthusiasm for undertaking thedesign and development of both analogue and digital sound -processingcircuitry in collaboration with the senior Experimental Officer and haverelevant experience. Salary at a point on the University's Grade 5 scale(£2889-£3367) dependent upon education, qualifications and experience.Applications in writing giving full details of age, education, qualificationsand experience together with names and addresses of two referees tothe Personnel Office, Old Shire Hall, Durham, by 28th February 1977

from whom further particulars are available.

AUDIO TESTENGINEERS

Allen & Heath Ltd and Brenell Engineeringare expanding their production of mixers

and tape recorders in North London.Test engineers with a good understandingof basic audio circuits are required forPCB and finished product test. This is anopportunity for capable, fast workers tojoin a young team. Bonus scheme inoperation. For interview call Ted Rook on

01-607 8271

SITUATIONS -WANTED*German Sound Engineer (27, degree) seeksjob in US Studio. Please contact: BernhardHandschuh, 7170 Schwab, Hall Neisseweg 46,W. Germany.

FOR SALE - PRIVATE*Revox G36, good condition, +tr, 34/7/. £100o.n.o. Ron Geesin, Heathfield (04352) 3994. B

INDEX TO DISPLAY ADVERTISERSA H 0Acoustical Manufacturing Co. Ltd. 9 Hayden Laboratories Ltd. ... 12 Otari ... 21

Acousmat Apollo 57 H.H. Electronics ... ... 6919

RAlice (Stancoil) Ltd. 8

Radford Laboratory Instruments Ltd. 47, 49Allen & Heath Ltd. 57Radio Recordings 29Amber ... 25 Ind. Tape Applications ... ... 13, 14, 15 Raindirk

Amity Schroeder 70 International Audio ... ... 17 R.E.W. ... 6, 8, 57, 70Ampex ... 7

A.P.R.S. 16

Audio & Design Recording Ltd. 4 JS

Audio Developments Ltd. ... 5 Brodr Jorgensen Ltd. ... ... 65Scenic Sounds 23

Audix . 45 Sescom Inc. ... 8

Sheffield Sound Centre ... 6

Shure Ltd. 59B K

S.M.E. Ltd. 31F. W. 0. Bauch Ltd. ... 33, 35, 41 Klark Teknik ... 43

Sonifex 29Brenell ... 29 Soundcraft Electronics Ltd. 55

L Squires, Roger ... 10

C Leevers-Rich 35Studio Equipment Services 6

Cadac (London) Ltd. IFC Levell Electronics Ltd. ... 39Surrey Electronics ... 56

C.A.E. Ltd. ... ... 33 Lexicon ... 32Swift of Wilmslow 53

Cetec Audio ... ... 11 London College of Furniture 70Craighall Studios ... 68 T

Trad Sales & Service ... ... 39

F M Trident Audio Dev. Ltd. ... 63

Feldon Audio Ltd. ... ... 53M.M. Electronics Tweed Audio ... ... 24

Future Film Developments ... 34 Macinnes Laboratories Ltd. ... 67

Magnetic Tapes ... ... 47

Midas Amplification Ltd. ... IBC Wadeys Tapes ... ... 29G Music Laboratories Ltd. ... 18 Ward -Beck Systems Ltd. ... 76Grahams Electronics ... ... 49 Mustang Communications ... 49 Webland Electronics ... ... 45

Published by Link House Publications Limited on behalf of the proprietors, Link House Holdings Limited, 10-12 South Crescent, Store Street, London W.C.1, and Printed byArthurs Press Limited, Woodchester, Stroud, Glos. GL5 5PB.

suP4

musicions:Beach Boys, Eluis Presley, Supertramp,Pink Floyd, Elton John, Chicago, YES.

sound hire.-

Sounds West u.s.n. Entec U.K.& u.s.n. Delicate Acoustics u.s.n.Clair Brothers u.s.n. Britannia Row U.K. Audio Analysts cnnnpn

54-56 Stanhope Street, London fW13EX. Tel: 01-388-7060Louis De Potesto, ARC, S.PR.L Rue Th. Decuyoer, 134,1200 Brussells, Belgium. Tel: 7-71-30-63

S

Ward -Beck portablesare going places.No matter how remote the location, traditional Ward -Beckstudio quality is now available from stock in the highlyportable M1002 console.The M1002 earned an enviable reputation as the greatperformer in the 1976 Summer and Winter Olympics.55 units were employed by ABC and CBC for networkcoverage of these historic events.The versatile M1203 offers increased input and output capability.'A combination of comprehensive monitoring facilities with anintegral front panel jack field make it ideal for mobile or studioinstallations where space is at a premium.Available from stock, the M1002 and M1203 come in a varietyof configurations designed to fit even the most modest budget.

(w MIN=

Tomorrow's Technology Today.

Ward -Beck Systems Ltd., 841 Progress Avenue, Scarborough,Ontario, Canada M1H 2X4.Telephone (416) 438-6550. Telex 06-23469.

WBS M1,00?: 10 channel consul'

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