Crown Com Tech 400 Owners Manual

K80636-23/95

CommercialAudioLL 32521C

Fire ProtectiveSignalingS5206

CommercialAudioE106377

120 VACNorth

AmericanUnits:

Approved forTHX TheatreSystems(CT-400 & 800)

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

Copyright 1995 by Crown International, Inc., P.O. Box 1000, Elkhart, Indiana 46515-1000 U.S.A.Telephone: 219-294-8000. Com-Tech amplifiers are produced by the Professional Audio Division ofCrown International, Inc. Trademark Notice: SmartAmp, MPX-6, SMX-6, AMB-5 and Groundedbridge are trademarks and Amcron, Crown, Techron, Com-Tech, IOC, ODEP, IQ System, P.I.P.and TEF are registered trademarks of Crown International, Inc. Other trademarks are the property oftheir respective owners.

Models:Com-Tech 200, 400, 800 & 1600Some models may be exported under the name Amcron.

WORLDWIDESUMMARY OF WARRANTY

The Crown Audio Division of Crown International, Inc., 1718 WestMishawaka Road, Elkhart, Indiana 46517-4095 U.S.A. warrants to you,the ORIGINAL PURCHASER and ANY SUBSEQUENT OWNER ofeach NEW Crown1 product, for a period of three (3) years from the dateof purchase by the original purchaser (the warranty period) that the newCrown product is free of defects in materials and workmanship, and wefurther warrant the new Crown product regardless of the reason forfailure, except as excluded in this Crown Warranty.1 Note: If your unit bears the name Amcron, please substitute it for thename Crown in this warranty.

ITEMS EXCLUDED FROM THIS CROWN WARRANTYThis Crown Warranty is in effect only for failure of a new Crown productwhich occurred within the Warranty Period. It does not cover any productwhich has been damaged because of any intentional misuse, accident,negligence, or loss which is covered under any of your insurancecontracts. This Crown Warranty also does not extend to the new Crownproduct if the serial number has been defaced, altered, or removed.

WHAT THE WARRANTOR WILL DOWe will remedy any defect, regardless of the reason for failure (except asexcluded), by repair, replacement, or refund. We may not elect refundunless you agree, or unless we are unable to provide replacement, andrepair is not practical or cannot be timely made. If a refund is elected, thenyou must make the defective or malfunctioning product available to usfree and clear of all liens or other encumbrances. The refund will be equalto the actual purchase price, not including interest, insurance, closingcosts, and other finance charges less a reasonable depreciation on theproduct from the date of original purchase. Warranty work can only beperformed at our authorized service centers. We will remedy the defectand ship the product from the service center within a reasonable timeafter receipt of the defective product at our authorized service center. Allexpenses in remedying the defect, including surface shipping costs tothe nearest authorized service center, will be borne by us. (You mustbear the expense of all taxes, duties and other customs fees whentransporting the product.)

HOW TO OBTAIN WARRANTY SERVICEYou must notify us of your need for warranty service not later than ninety(90) days after expiration of the warranty period. All components must beshipped in a factory pack. Corrective action will be taken within areasonable time of the date of receipt of the defective product by ourauthorized service center. If the repairs made by our authorized servicecenter are not satisfactory, notify our authorized service centerimmediately.DISCLAIMER OF CONSEQUENTIAL AND INCIDENTAL DAMAGESYOU ARE NOT ENTITLED TO RECOVER FROM US ANYINCIDENTAL DAMAGES RESULTING FROM ANY DEFECT IN THENEW CROWN PRODUCT. THIS INCLUDES ANY DAMAGE TOANOTHER PRODUCT OR PRODUCTS RESULTING FROM SUCH ADEFECT.

WARRANTY ALTERATIONSNo person has the authority to enlarge, amend, or modify this CrownWarranty. This Crown Warranty is not extended by the length of timewhich you are deprived of the use of the new Crown product. Repairs andreplacement parts provided under the terms of this Crown Warranty shallcarry only the unexpired portion of this Crown Warranty.

DESIGN CHANGESWe reserve the right to change the design of any product from time to timewithout notice and with no obligation to make corresponding changes inproducts previously manufactured.

LEGAL REMEDIES OF PURCHASERNo action to enforce this Crown Warranty shall be commenced later thanninety (90) days after expiration of the warranty period.THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERS

CONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.

Telephone: 219-294-8200. Facsimile: 219-294-8301 9/90

YEAR3YEAR3

NORTH AMERICASUMMARY OF WARRANTY

The Crown Audio Division of Crown International, Inc., 1718 West MishawakaRoad, Elkhart, Indiana 46517-4095 U.S.A. warrants to you, the ORIGINALPURCHASER and ANY SUBSEQUENT OWNER of each NEW Crownproduct, for a period of three (3) years from the date of purchase by the originalpurchaser (the warranty period) that the new Crown product is free of defectsin materials and workmanship, and we further warrant the new Crown productregardless of the reason for failure, except as excluded in this CrownWarranty.

ITEMS EXCLUDED FROM THIS CROWN WARRANTYThis Crown Warranty is in effect only for failure of a new Crown product whichoccurred within the Warranty Period. It does not cover any product which hasbeen damaged because of any intentional misuse, accident, negligence, orloss which is covered under any of your insurance contracts. This CrownWarranty also does not extend to the new Crown product if the serial numberhas been defaced, altered, or removed.

WHAT THE WARRANTOR WILL DOWe will remedy any defect, regardless of the reason for failure (except asexcluded), by repair, replacement, or refund. We may not elect refund unlessyou agree, or unless we are unable to provide replacement, and repair is notpractical or cannot be timely made. If a refund is elected, then you must makethe defective or malfunctioning product available to us free and clear of all liensor other encumbrances. The refund will be equal to the actual purchase price,not including interest, insurance, closing costs, and other finance charges lessa reasonable depreciation on the product from the date of original purchase.Warranty work can only be performed at our authorized service centers or atthe factory. We will remedy the defect and ship the product from the servicecenter or our factory within a reasonable time after receipt of the defectiveproduct at our authorized service center or our factory. All expenses inremedying the defect, including surface shipping costs in the United States,will be borne by us. (You must bear the expense of shipping the productbetween any foreign country and the port of entry in the United States and alltaxes, duties, and other customs fees for such foreign shipments.)

HOW TO OBTAIN WARRANTY SERVICEYou must notify us of your need for warranty service not later than ninety (90)days after expiration of the warranty period. All components must be shippedin a factory pack, which, if needed, may be obtained from us free of charge.Corrective action will be taken within a reasonable time of the date of receiptof the defective product by us or our authorized service center. If the repairsmade by us or our authorized service center are not satisfactory, notify us orour authorized service center immediately.

DISCLAIMER OF CONSEQUENTIAL AND INCIDENTAL DAMAGESYOU ARE NOT ENTITLED TO RECOVER FROM US ANY INCIDENTALDAMAGES RESULTING FROM ANY DEFECT IN THE NEW CROWNPRODUCT. THIS INCLUDES ANY DAMAGE TO ANOTHER PRODUCT ORPRODUCTS RESULTING FROM SUCH A DEFECT. SOME STATES DONOT ALLOW THE EXCLUSION OR LIMITATIONS OF INCIDENTAL ORCONSEQUENTIAL DAMAGES, SO THE ABOVE LIMITATION OREXCLUSION MAY NOT APPLY TO YOU.

WARRANTY ALTERATIONSNo person has the authority to enlarge, amend, or modify this Crown Warranty.This Crown Warranty is not extended by the length of time which you aredeprived of the use of the new Crown product. Repairs and replacement partsprovided under the terms of this Crown Warranty shall carry only the unexpiredportion of this Crown Warranty.

DESIGN CHANGESWe reserve the right to change the design of any product from time to timewithout notice and with no obligation to make corresponding changes inproducts previously manufactured.

LEGAL REMEDIES OF PURCHASERTHIS CROWN WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, YOUMAY ALSO HAVE OTHER RIGHTS WHICH VARY FROM STATE TOSTATE. No action to enforce this Crown Warranty shall be commenced laterthan ninety (90) days after expiration of the warranty period.

THIS STATEMENT OF WARRANTY SUPERSEDES ANY OTHERSCONTAINED IN THIS MANUAL FOR CROWN PRODUCTS.

Telephone: 219-294-8200. Facsimile: 219-294-8301 9/90

THREE YEARFULL WARRANTY

TO PREVENT ELECTRIC SHOCK DONOT REMOVE TOP OR BOTTOM

COVERS. NO USER SERVICEABLEPARTS INSIDE. REFER SERVICINGTO QUALIFIED SERVICE PERSON-NEL. DISCONNECT POWER CORDBEFORE REMOVING REAR INPUT

MODULE TO ACCESS GAIN SWITCH.

C A U T I O NRISK OF ELECTRIC SHOCK

DO NOT OPEN

PRVENIR LE CHOCLECTRIQUE NENLEVEZPAS LES COUVERCLES.

RIEN DES PARTIESUTILES LINTRIEUR.

DBRANCHER LA BORNEAVANT DOUVRIR LA

MODULE EN ARRIRE.

A V I SRISQUE DE CHOC LECTRIQUE

NOUVREZ PAS

WARNINGTO REDUCE THE RISK OF ELECTRIC

SHOCK, DO NOT EXPOSE THISEQUIPMENT TO RAIN OR MOISTURE!

Magnetic FieldCAUTION! Do not locate sensitive high-gain equipmentsuch as preamplifiers or tape decks directly above orbelow the unit. Because this amplifier has a high powerdensity, it has a strong magnetic field which can inducehum into unshielded devices that are located nearby.The field is strongest just above and below the unit.

If an equipment rack is used, we recommend locatingthe amplifier(s) in the bottom of the rack and the pream-plifier or other sensitive equipment at the top.

Printed onrecycled paper.

The lightning bolttriangle is used toalert the user to therisk of electric shock.

WATCH FOR THESE SYMBOLS:The exclamation pointtriangle is used to alert theuser to important operatingor maintenance instructions.

The information furnished in this manual does not include all of the details of design, production, or variationsof the equipment. Nor does it cover every possible situation which may arise during installation, operation ormaintenance. If your unit bears the name Amcron, please substitute it for the name Crown in this manual.If you need special assistance beyond the scope of this manual, please contact our Technical Support Group.

Crown Audio Division Technical Support Group57620 C.R. 105, Elkhart, Indiana 46517 U.S.A.

Phone: 219-294-8200 Fax: 219-294-8301

Toll Free in Canada, Puerto Rico, the UnitedStates & Virgin Islands: 1-800-342-6939

FIRE PROTECTIVE SIGNALINGTHIS AMPLIFIER IS UL-LISTED FOR FIRE

PROTECTIVE SIGNALING SYSTEMS. REFER TO SECTION 9 FOR DETAILS

CAUTIONCLASS 1 OUTPUT WIRING REQUIRED.

Com-Tech 200/400/800/1600 Power Amplifiers

CONTENTS1 Welcome ........................................................................... 7

1.1 Unpacking................................................................. 71.2 Features .................................................................... 7

2 Facilities ............................................................................ 8

3 Installation ....................................................................... 103.1 Mounting.................................................................. 103.2 Cooling .................................................................... 10

3.2.1 Cooling for Units without Internal Fans ........... 113.2.2 Additional Cooling for Units with Internal Fans 11

3.3 Wiring ...................................................................... 123.3.1 Mode of Operation ........................................ 123.3.2 Input Connection .......................................... 173.3.3 Output Connection ....................................... 183.3.4 Additional Load Protection ........................... 20

3.4 AC Mains Power ...................................................... 21

4 Operation ........................................................................ 224.1 Precautions ............................................................. 224.2 Indicators ................................................................ 224.3 Protection Systems ................................................. 23

4.3.1 ODEP ............................................................ 234.3.2 Standby Mode .............................................. 244.3.3 Transformer Thermal Protection ................... 244.3.4 Circuit Breaker .............................................. 24

4.4 Controls ................................................................... 254.5 Filter Cleaning ......................................................... 25

5 Technical Information ...................................................... 265.1 Overview ................................................................. 265.2 Circuit Theory .......................................................... 26

5.2.1 Dual Operation ............................................. 265.2.2 Bridge-Mono Operation ................................ 285.2.3 Parallel-Mono Operation ............................... 28

6 Specifications .................................................................. 29

7 AC Power Draw and Thermal Dissipation ....................... 42

8 Accessories ..................................................................... 448.1 P.I.P. Modules ......................................................... 448.2 Cooling Fan Option (120 VAC, 60 Hz only) ............. 468.3 Constant Voltage Computer .................................... 46

9 Fire Protective Signaling ................................................. 47

10 Service ............................................................................ 4810.1 Worldwide Service ................................................. 4810.2 North American Service ......................................... 48

10.2.1 Service at a North American Service Center 4810.2.2 Factory Service ............................................ 48


ILLUSTRATIONS1.1 Com-Tech Amplifiers (120 VAC, 60 Hz Units) ........................... 62.1 Front Facilities ........................................................................... 82.2 Rear Facilities ............................................................................ 93.1 Mounting Dimensions .............................................................. 103.2 Top View of a Rack-Mounted Unit ........................................... 113.3 Extra Cooling with a Rack-Mounted Blower ............................ 123.4 Wiring for Dual 8/4 Ohm Mode ................................................ 133.5 Wiring for Dual 70 Volt Mode................................................... 143.6 Wiring for Bridge-Mono 70 Volt Mode (140 Volt Output) ......... 153.7 Wiring for Parallel-Mono 70 Volt, Bridge-Mono 8/4 Ohm

and Parallel-Mono 8/4 Ohm Modes......................................... 163.8 Unbalanced Input Wiring ........................................................ 173.9 Balanced Input Wiring ............................................................. 173.10 Subsonic Filter Capacitor Values ............................................ 173.11 Unbalanced RFI Filters ............................................................ 183.12 Balanced RFI Filters ................................................................ 183.13 Wire Size Nomograph ............................................................. 193.14 Inductive Load (Transformer) Network .................................... 203.15 Loudspeaker Fuse Nomograph .............................................. 204.1 ODEP, IOC and Signal Presence Indicator States .................. 234.2 Input Sensitivity Switch ............................................................ 255.1 Circuit Block Diagram ............................................................. 276.1 Com-Tech 200 Minimum Power Matrix ................................... 326.2 Com-Tech 400 Minimum Power Matrix ................................... 336.3 Com-Tech 800 Minimum Power Matrix ................................... 346.4 Com-Tech 1600 Minimum Power Matrix ................................. 356.5 Com-Tech 200 Maximum Power Matrix .................................. 366.6 Com-Tech 400 Maximum Power Matrix .................................. 376.7 Com-Tech 800 Maximum Power Matrix .................................. 386.8 Com-Tech 1600 Maximum Power Matrix ................................ 396.9 Typical Frequency Response ................................................. 406.10 Typical Damping Factor .......................................................... 406.11 Typical Output Impedance...................................................... 406.12 Typical Phase Response ......................................................... 416.13 Typical Crosstalk ..................................................................... 417.1 Com-Tech 200 Power Draw, Current Draw and

Thermal Dissipation at Various Duty Cycles ........................... 427.2 Com-Tech 400 Power Draw, Current Draw and



Thermal Dissipation at Various Duty Cycles ........................... 438.1 Installing a P.I.P. Module ......................................................... 448.2 Cooling Fan Option ................................................................. 468.3 Cooling Fan Assembly ............................................................ 46


Fig. 1.1 Com-Tech Amplifiers (120 VAC, 60 Hz Units)

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF


1 WelcomeCongratulations on your purchase of a Com-Techcommercial power amplifier. The Com-Tech series is acomplete family of amplifiers with a wide range ofpower output capabilities. Com-Tech amplifiers candirectly drive constant voltage lines, so you canavoid the expense, distortion and insertion loss associ-ated with step-up transformers for distributedloudspeaker systems. Com-Tech amplifiers also utilizeCrowns patented ODEP protection circuitry whichkeeps the amplifier working under severe conditionsthat would shut down a lesser amplifier. All Com-Techamplifiers feature Crowns exclusive P.I.P. (Program-mable Input Processor) expansion system. The P.I.P.expansion system makes it easy to tailor your amplifierto a specific application or to add future technology asit develops (see Section 8 for a list of available P.I.P.s).

This manual will help you successfully install and useyour new Com-Tech amplifier. Please read all instruc-tions, warnings and cautions. Be sure to read Section3.3.1 if you plan to use the amplifier in one of its twomono modes, or if you plan to drive constant voltagelines. Also for your protection, please send in your war-ranty registration card today and save your bill of saleas it is your official proof of purchase.

protection circuitry and grounded bridge outputstages combine to provide performance and reliabilitythat surpass the other more traditional designs. Hereare some more of your amplifiers impressive features:

Crowns patented ODEP (Output Device EmulationProtection) circuitry detects and compensates foroverheating and overload to keep the amplifier workingwhen others would fail.

Crowns grounded bridge design delivers incrediblevoltage swings without using stressful output transistorconfigurations like conventional amplifiers. The resultsare lower distortion and superior reliability.

IOC (Input/Output Comparator) circuitry immediatelyalerts you if any type of distortion exceeds 0.05%. Weprovide this feature so you will have real-time proof ofdistortion-free performance.

P.I.P. (Programmable Input Processor) connectoraccepts accessories that tailor the amplifier to suitspecific applications.

Drives constant voltage lines without lossy, distortion-producing step-up transformers.

Two mono modes (Bridge-Mono and Parallel-Mono) fordriving a wide range of load impedances.

Very low harmonic and intermodulation distortion givethe best dynamic transfer function in the industry.

Superior damping factor delivers maximum loud-speaker motion control for a clean, accurate low end.

Superb crosstalk characteristics and a separatevoltage supply for each channel make it possible totreat each channel like a separate amplifier.

Full protection from shorted, open and mismatchedloads, general overheating, DC and high-frequencyoverloads. Full internal fault protection.

Efficient heat sinks and three-speed fan dissipate heatquickly and evenly for extra amplifier protection andextended component life. (The fan is an option for120 VAC, 60 Hz Com-Tech 200s.)

Barrier blocks are provided for input and outputconnections.

Internal three-position input sensitivity switch providessettings of 0.775 volts for full standard 1 kHz 8/4 ohmpower, 0.775 volts for full standard 1 kHz 70 volt power,and 26 dB voltage gain.

Mounts in a standard 19 inch (48.3 cm) equipment rack(units can also be stacked).

Three year No-Fault full warranty completely protectsyour investment and guarantees its specifications.

1.1 UnpackingPlease unpack and inspect your new amplifier for anydamage that may have occurred during transit. If dam-age is found, notify the transportation company imme-diately. Only you, the consignee, may initiate a claimfor shipping damage. Crown will be happy to cooper-ate fully as needed. Save the shipping carton as evi-dence of damage for the shippers inspection.

Even if the unit arrived in perfect condition, as most do,save all packing materials so you will have them if youever need to transport the unit. NEVER SHIP THEUNIT WITHOUT THE FACTORY PACK.

1.2 FeaturesCom-Tech amplifiers use cutting edge technology andminiaturized design to provide the highest power andvalue for its size, weight and price. They offer numer-ous advantages over conventional designs and pro-vide benefits you cant get in amplifiers from any othermanufacturer. For example, Crowns patented ODEP


2 FacilitiesA. Filter GrilleA metal grille supports and protects the dust filter (B).To clean the dust filter, detach the grille by removingthe screws that fasten it in place.

B. Dust FilterThe dust filter removes large particles from air drawnby the cooling fan. (The fan is an option for 120 VAC,60 Hz Com-Tech 200s.) Check the filter regularly toprevent clogging (see Section 4.5).

C. ODEP IndicatorsDuring normal operation of the Output Device Emula-tion Protection circuitry, these green indicators glowbrightly to show the presence of reserve thermal-dy-namic energy. They dim proportionally as energy re-serves decrease. In the rare event that energyreserves are depleted, the indicators turn off andODEP proportionally limits output drive so the amplifiercan safely continue operating even under severe con-ditions. These indicators can also help to identify moreunusual operating problems (see Section 4.2).

D. IOC IndicatorsThe yellow IOC (Input/Output Comparator) indicatorsserve as sensitive distortion indicators to provide proofof distortion-free performance. Under normal condi-tions, the indicators remain off. They light up if the out-put waveform differs from the input by 0.05% or more(see Section 4.2). Note: The channel 2 IOC indicatorwill stay on in Parallel-Mono mode.

E. Signal Presence Indicators (SPI)The signal presence indicators flash synchronouslywith the amplifiers audio output (see Section 4.2).

F. Enable IndicatorThis indicator lights when the amplifier has been en-abled or turned on, and AC power is available (seeSection 4.2).

G. Enable SwitchThis rocker switch is used to turn the amplifier on andoff. When turned on, the output is muted for about fourseconds to protect your system from turn-on tran-sients. Delay times vary slightly from one unit to thenext, so there is always a certain amount of random-ness in the turn-on timing of multiple units. In addition,turn-on occurs at zero crossing of the AC waveform, soCom-Tech amplifiers rarely need a power sequencer.(To change the turn-on delay time, contact CrownsTechnical Support Group.) See Section 4.4.

H. Power CordAll 120 VAC, 60 Hz North American units have aNEMA 5-15P plug with an integral voltage presencelamp. These units include a 16 gauge power cord withCom-Tech 200s and 400s, and a 14 gauge cord withCom-Tech 800s and 1600s. Other units have an ap-propriate power cord and plug for the required ACvoltage. Refer to Section 7 for more information onpower usage.

Fig. 2.1 Front Facilities

P OW ER

ODEP

IOC

SPI

ENABLE

CH1 CH2 OFF

A B EDC CDE F G


Fig. 2.2 Rear Facilities

I. Reset SwitchThis reset switch is used to reset the circuit breakerthat protects the power supplies from overload (seeSections 4.3.4 and 4.4).

J. Dual/Mono SwitchSlide this switch to the center for Dual (two-channel)mode, to the left for Parallel-Mono mode or to the rightfor Bridge-Mono mode. WARNING: Do not change thisswitch unless the amplifier is turned off. Do not attemptto use the Bridge-Mono or Parallel-Mono modes unlessboth output mode switches (N) are set the same. Also,be sure to follow the installation requirements for eachmode (see Section 3.3.1).

K. P.I.P. ModuleThe standard P.I.P.-BB is included with your amplifier.It provides barrier block input connectors. Other P.I.P.modules can be used in place of the P.I.P.-BB to pro-vide additional features that customize the amplifier fordifferent applications (see Section 8 for available P.I.P.modules).

Input Sensitivity SwitchThe three position input sensitivity switch located in-side the amplifier is accessed by removing the P.I.P.module. It is set at the factory to 0.775 volts for stan-dard 1 kHz power into 8 ohms. It can also be set to0.775 volts for standard 1 kHz output in 70 volt mode,or a standard voltage gain of 26 dB (see Section 4.4).

L. Level ControlsEach channels output level can be adjusted accu-rately using the 22 position detented level controls onthe back panel. A Lexan cover is also included thatcan be used to prevent tampering (see Section 4.4).

M. Balanced Barrier Block InputsThe P.I.P.-BB is included in the standard configuration.It provides a balanced barrier block with three termi-nals for each input channel. (XLR connectors are alsoavailablesee Section 8.1.)

N. Output Mode SwitchesThe output mode switches are used to configure eachchannel independently for either 8/4 ohm loads or70 volt (constant voltage) lines. WARNING: Do notchange these switches unless the amplifier is off. Donot attempt to use the Bridge-Mono or Parallel-Monomodes unless these switches are set the same. Also,be sure to follow the special installation requirementsfor each mode (see Section 3.3.1).

O. Output Barrier BlockA barrier block with four terminals is provided for out-put connection. Output wiring will vary depending onthe selected dual/mono mode and whether 70 volt out-put will be used (see Section 3.3.1).

BB

ProgrammableInput Processor (P.I.P.)

+C H - 2 I N P U T

+C H - 1 I N P U T

PUSH TO RESET

CAUTION: TURN OFF AMPLIFIER BEFORE CHANGING THIS SWITCH!

DUAL

BRIDGEMONO

PARALLELMONOCAUTION: BOTH CHANNELS MUST

BE CONFIGURED THE SAME (8/4 OHMOR 70 VOLT) BEFORE USING EITHERBRIDGE- OR PARALLEL-MONO MODE.

MODEL: COM-TECH 200 AC VOLTS: 120 AMPS: 3.5 60 Hz

RATED OUTPUT: 150 W/CH INTO 4 OHMSAT 1 KHz WITH 0.1% OR LESS THD.

MAXIMUM OUTPUT: 200 W/CH INTO 4OHMS AT 1 KHz WITH 0.1% OR LESS THD.

MODEL: COM-TECH 400 SERIES AC VOLTS: 120 AMPS: 5.5 60 Hz

REFER TO OWNER'S MANUAL K80636-2FOR FIRE PROTECTIVE SIGNALING USE.

REFER TO USER'S MANUAL K80548-9FOR FIRE PROTECTIVE SIGNALING USE.

0dB.5

1234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32

REG. U.S. PAT. OFF.4,330,8094,611,180

THIS AMPLIFIER IS EQUIPPED WITH SELECTABLE INPUT SENSITIVITY. REMOVE P.I.P. MODULE TO ACCESS SENSITIVITY SWITCH.

CH-2 CH-1INPUT ATTENUATION

+ +

70VOLT

8/4OHM

70VOLT

8/4OHM

CH-2 OUTPUT CH-1 OUTPUT

BRIDGE-MONO: 1) TURN AMPLIFIEROFF. 2) SET DUAL/MONO SWITCH TOBRIDGE-MONO. 3) OUTPUT ACROSS +TERMINALS ONLY (CH-1 IS POSTIVE).

PARALLEL-MONO: 1) TURN AMPLIFIEROFF. 2) SET DUAL/MONO SWITCH TOPARALLEL-MONO. 3) ADD JUMPER (14 GAGEOR LARGER) ACROSS THE + TERMINALS4) OUTPUT ACROSS CH-1 TERMINALS ONLY.

IMPORTANT:CLASS 1 OUTPUT WIRING REQUIRED. INTERNATIONAL, INC.ELECTRONIC EQUIPMENT

ELKHART, IN 46517MADE IN U.S.A.

SERIAL NUMBER

0000000000

PRESS

R E S E T

H J LK OMI L N


3 InstallationThis section covers basic Com-Tech installation pro-cedures. If your amplifier will be used in a Fire Protec-tive Signaling application, refer to Section 9 as well.

3.1 MountingCom-Tech amplifiers are designed for standard19 inch (48.3 cm) rack mounting or stacking without acabinet. In a rack, it is best to mount units directly ontop of each other. This provides the most efficient airflow and support. If the rack will be transported, werecommend that you fasten the amplifiers back panelsecurely to the rack to help support the units weight.

All Com-Tech amplifiers are 19 inches (48.3 cm) wide,16 inches (40.6 cm) deep, and 0.25 inches (0.6 cm) infront of the mounting surface. As you can see in Fig-ure 3.1, Com-Tech amplifiers vary in their vertical di-mensions. Figure 3.1 labels the different heights as A,B and C. These letters correspond to the list that fol-lows showing Com-Tech models and their vertical di-mensions.

Height A: 3.5 inches (8.9 cm)Models: Com-Tech 200 (All)

Com-Tech 400 (North American)

Height B: 5.25 inches (13.3 cm)Models: Com-Tech 400 (100/120 VAC, 50/60 Hz)

Com-Tech 400 (220/240 VAC, 50/60 Hz)Com-Tech 800 (All)

Height C: 7 inches (17.8 cm)Model: Com-Tech 1600 (All)

3.2 CoolingIt is important to understand cooling considerationswhen installing a Com-Tech amplifier. First, neverblock the amplifiers front or side air vents. This cancause poor air flow and may result in overheating. Ifthe amplifier is rack-mounted, its sides should be atleast 2 inches (5 cm) away from the cabinet (seeFigure 3.2). Also, open spaces in the front of the rackshould be covered with blank panels to preventimproper air flow. Otherwise, heated air from the sideexhaust vents can be drawn into the front air intakewhich may greatly reduce the cooling systemseffectiveness.

The real air flow requirement for a Com-Tech amplifierdepends on many things, but the most important factoris average (RMS) output power. Air flow requirementsincrease as output power increases, so anything that

C: 7 in

(17.8 cm)

P OWER

ODEP

IOC

SPI

ENABLE

CH1

CH2

OFFB: 5.

25 in

(13.3 cm)

A: 3.5 in

(8.9 cm)

19 in

(48.3 cm)

16 in(40.6 cm)

Fig. 3.1 Mounting Dimensions


than 400 btu (100 kcal) per hour per unit will need ad-ditional cooling. If you want to test your amplifier forsufficient cooling in the real world, an easy way is toobserve the ODEP indicators while the amplifier is op-erating under worst-case conditions. If the indicatorsdim, additional cooling is recommended.

There are at least three ways to provide extra coolingfor an amplifier that does not have an internal fan. Themost effective method is to install an internal fan whichis available from Crown as an accessory (see Sec-tion 8.2). If you know in advance that an internal fan isneeded, you can order the Com-Tech 200BF which in-cludes a factory-installed fan.

A rack-mounted blower or an air conditioner can alsobe used to provide extra cooling. In some situations,you may find it practical to use these methods withoutinstalling a fan in each amplifier. However, we gener-ally recommend that you use the internal fans becausethey provide the most efficient cooling, and are activeonly when needed. Amplifiers that already have inter-nal fans can also take advantage of a rack-mountedblower or air conditioner, so these approaches will bediscussed in the section that follows.

3.2.2 Additional Cooling for Units with Internal FansIf multiple amplifiers will be operated under demand-ing conditions (such as driving loads less than4 ohms), or if air flow through the rack will be restricted,you should verify that the total air flow through the rackwill be sufficient. As described in Section 3.2.1, suffi-cient air flow can be tested in the real world by observ-ing the ODEP indicators while operating underworst-case conditions. If the indicators dim, coolingcan be improved by reducing air restrictions, installinga rack-mounted blower, or using an air conditioner.

Many things can cause air flow restrictions, includingimproper mounting, bunched up power cords, closedrack doors, and clogged dust filters. A Com-Tech am-plifier should be mounted in a way that allows sufficientair flow into the front intakes, out the side exhaustvents, and out the back of the rack. If your rack has afront door, it is usually best to leave it open and avoidblocking the air intakes. If this is impossible, supple-ment the air flow by mounting a grille in the door or witha rack-mounted blower. If you install a grille in the door,we recommend wire grilles over perforated panels be-cause wire tends to cause less air restriction (perfo-rated panels cause a minimum air restriction of 40%).

A better choice for increasing the air flow behind arack cabinet door is to use a squirrel cage blower.

AIRFLOW

AIR FLOW

RACKCABINET

16 in40.6 cm

2 in(5 cm)MIN.

17 in43.2 cm

AIRFLOW

AMPLIFIER(TOP VIEW)

IMPORTANT: Be sure the back ofthe amplifier is supported.

Fig. 3.2 Top View of a Rack-Mounted Unit

affects output power also affects the required air flow.

Average output power is mainly affected by threethings: (1) duty cycle of the input signal, (2) load im-pedance, and (3) rated output power. First, as the dutycycle of the input signal increases, the average outputpower level increases. For example, the amplifier willneed more air flow with a rock n roll input signal thanwith infrequent paging. Second, as the load imped-ance of a connected loudspeaker gets smaller, morecurrent will flow across the load which effectively in-creases output power. This means you can expect theamplifier to require more air flow with a 2 ohm load thanwith a 4 ohm load. Finally, an amplifier that is rated forhigher power output is usually used at higher averageoutput levels. So a Com-Tech 1600 delivering full out-put will require more air flow than a Com-Tech 200.These relationships and the resulting thermal dissipa-tion levels are defined mathematically in Section 7.

3.2.1 Cooling for Units without Internal FansAll units have a three-speed on-demand cooling fanexcept for the North American Com-Tech 200. Forced-air cooling may not be needed for applications with alow duty cycle such as paging or background music.This is why the North American Com-Tech 200 isusually provided without a fan.

If you will be using a North American Com-Tech 200 ina high temperature environment, or at full power forsustained periods, you can anticipate that additionalcooling will be needed. It may also be helpful to usethe information in Section 7 to estimate the amplifiersthermal dissipation for your application. In general, aNorth American Com-Tech 200 that dissipates more


ducing the temperature of the air circulated throughthe rack. If you intend to install air conditioning for youramplifiers, you may want to use Section 7 to determinethe hourly thermal dissipation of your system.

3.3 WiringFigures 3.4 through 3.7 show common ways to install aCom-Tech amplifier in a sound system. Input and out-put terminals are located on the back panel. Pleaseuse care when making connections, selecting signalsources and controlling the output level. The load yousave may be your own! Crown assumes no liability fordamaged loads resulting from careless amplifier useor deliberate overpowering.

CAUTION: Always disconnect the AC power and turnthe level controls off when making or breaking connec-tions. This is very important when loudspeakers areconnected because it reduces the chance of loudblasts that can cause loudspeaker damage.

3.3.1 Mode of OperationProper wiring depends on how you configure your am-plifier. First, each output channel can be indepen-dently configured to drive step-down transformers in adistributed constant voltage loudspeaker system(70 volt mode) or loudspeakers that do not have step-down transformers (8/4 ohm mode). Second, the am-plifier can be configured for Dual, Bridge-Mono orParallel-Mono modes. Various combinations of thesemodes are possible, so be sure to note any specialwiring requirements for the mode you will be using.

70VOLT

8/4OHM

7 0 V O L TThe 70 volt output mode is used to drive constant volt-age lines without expensive step-up transformers.Avoiding the use of step-up transformers not onlysaves money, but it also eliminates the distortion andinsertion loss caused by this type of transformer.

Setting up 70 volt mode is easy. Turn off the amplifier,then slide the recessed output mode switches to theright (as you face the back panel).

If Bridge-Mono mode is used with 70 volt output, theamplifier will actually deliver 140 volts (more informa-tion is provided later in this section). To effectively usethis mode, you may need to cross-reference power rat-ings for the step-down transformer taps using Crownsconstant voltage computer (see Section 8.3).

BLOWER(OPTION 2)

BLOWER(OPTION 1)

AIRFLOW

FRONTOF

RACK

DOOR

AIRFLOW

EQUIPMENTRACK

(SIDE VIEW)

Mount the blower at the bottom of the rack so it blowsoutside air into the space between the door and thefront of the amplifiers, pressurizing the chimney be-hind the door (Figure 3.3, Option 1). The blower shouldnot blow air into or take air out of the space behind theamplifiers. For racks without a front door, you canevacuate the rack by mounting the blower at the top ofthe rack, so that air blows out the back (Figure 3.3,Option 2).

You can estimate the required air flow for a rack byadding together the maximum required air flow ratingsof the individual units. The internal fan in a Com-Tech200 (if installed), 400 and 800 can move up to 35 cu-bic feet (1 cubic meter) of air per minute, while the in-ternal fan in a Com-Tech 1600 can move up to 65cubic feet (1.8 cubic meters) per minute. If youmounted one of each Com-Tech model in a rack,worst-case conditions would require 170 cubic feet(4.7 cubic meters) of air flow through the rack everyminute (3 x 35 cubic feet + 65 cubic feet = 170 cubicfeet).

Air flow restrictions may also result if the air filter be-comes clogged. If the air supply is unusually dusty,you can help prevent rapid loading of the units air filterby pre-filtering the air using commercial furnace filters.And when needed, the unit's filter can be cleaned withmild dish detergent and water (see Section 4.5).

The final method for increased cooling is to use airconditioning. Air conditioning is rarely a necessity be-cause internal fans and rack-mounted blowers almostalways provide enough air flow for even the most ex-treme conditions. Still, air conditioning can help by re-

Fig. 3.3 Extra Cooling with a Rack-Mounted Blower


this, the input sensitivity should be set to 0.775 volts for70 volt output (see Section 4.4). Again, you must al-ways configure both channels the same when usingBridge-Mono or Parallel-Mono modes.

Because of the way Com-Tech amplifiers are de-signed, they can actually be used to directly drive con-stant voltage lines in 8/4 ohm mode. Being able to uselower constant voltage levels can be very convenient ifbuilding codes or other obstacles do not permit higherconstant voltage levels. When 8/4 ohm mode is usedto drive a distributed loudspeaker system, the constantvoltage output varies with the output power rating ofthe amplifier. With 8/4 ohm output in Dual or Parallel-Mono mode, the Com-Tech 200 can drive a 25 voltline, the Com-Tech 400 can drive a 35 volt line, theCom-Tech 800 can drive a 50 volt line, and theCom-Tech 1600 can drive a 70 volt line. Using Bridge-Mono mode, these voltage levels are doubled for asingle channel. Again, to effectively use different con-stant voltage levels, you may need to cross-referencethe ratings for the step-down transformers taps usingCrowns constant voltage computer (see Section 8.3).

BRIDGEMONO

DUAL

PARALLELMONO

D U A LDual mode lets each amplifier channel work indepen-dently like a dual mono or stereo amplifier. And if youselect both Dual mode and 70 volt output, each output

WARNING: The output mode switches must be set thesame (8/4 ohm or 70 volt mode) when operating inBridge-Mono or Parallel-Mono mode.

When connecting a 70 volt step-down transformer, donot exceed its power rating. Too much power cansaturate a transformer and cause it to appear as ashort circuit to the amplifier. If this happens, no dam-age should occur, but the amplifier may run less effi-ciently.

70VOLT

8/4OHM

8 / 4 O H M8/4 ohm mode is commonly used to drive loudspeak-ers with impedances from 2 to 16 ohms. When usingthis output mode, appropriate load impedances willdepend on the dual/mono mode that you select. Theavailable dual/mono modes (Dual, Bridge-Mono andParallel-Mono) will be described in sections that follow.

Configuring your amplifier for 8/4 ohm mode isstraightforward. Turn off the amplifier, then slide theoutput mode switches to the left (as you face the backpanel).

When the amplifier is set up for two-channel (Dualmode) operation, it is possible to configure one outputchannel for 8/4 ohm operation and the other for 70 voltoperation. If you plan to use different output modes like

Fig. 3.4 Wiring for Dual 8/4 Ohm Mode

MIXER

LOUDSPEAKERS

Com-Tech Amplifier

+

+

CHANNEL 1

CHANNEL 2

CHANNEL 1

CHANNEL 2

DUAL 8/4 OHM MODE(BOTH CHANNELS) TURN OFF THE AMP LIFIERBEFORE CHANGING

THE DUAL/MONO SWITCH.

70VOLT

70VOLT

8/4OHM

8/4OHM

CH1CH2

TURN OFF THE AMPLIFIERBEFORE CHANGING THE

OUTPUT MODE SWITCHES.

BRIDGEMONO

DUAL

PARALLELMONO

BB


+C H - 2 I N P U T

+C H - 1 I N P U T

PRESS

R E S E T

PUSH TO RESET

CH-2 CH-10dB

.51

234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32


140 volt distributed loudspeaker systems. If you will beusing 140 volt output, you may need to cross-refer-ence the ratings of the step-down transformer tapswith Crowns constant voltage computer (see Section8.3). If you need a single channel with higher power todrive a 70 volt line, use Parallel-Mono mode.

WARNING: Both channels must be configured for thesame output mode (8/4 ohm or 70 volt) before switch-ing to Bridge-Mono mode.

Bridge-Mono wiring is very different from the othermodes and requires special attention. First, turn theamplifier off. Then select Bridge-Mono mode by slidingthe dual/mono switch to the right (as you face the backpanel). Both outputs will receive the signal from chan-nel 1 with the output of channel 2 inverted so it can bebridged with the channel 1 output. DO NOT USE THECHANNEL 2 INPUT or the signal level and quality maybe greatly degraded. Also, keep the channel 2 levelcontrol turned down completely (counterclockwise).

Note: The channel 2 input jack and level control are notdefeated in Bridge-Mono mode. A signal feedingchannel 2 will work against the channel 1 signal, andusually results in distortion and inefficient operation.

Connect the load across the two positive (+) output ter-

channel can be used to drive a 70 volt line. Installationis intuitive: input channel 1 feeds output channel 1,and input channel 2 feeds output channel 2.

To put the amplifier into Dual mode, turn it off, slide thedual/mono switch to the center position, and properlyconnect the output wiring. Be sure to observe correctloudspeaker polarity (see Figure 3.4) and be carefulnot to short the two outputs.

CAUTION: Never tie an amplifiers outputs together di-rectly, and never parallel them with the output of an-other amplifier. Such connections do not result inincreased output power, but may cause overheatingand premature activation of the protection circuitry.

Note: To parallel multiple amplifiers for fail-safe redun-dancy, contact Crowns Technical Support Group.

BRIDGEMONO

DUAL

PARALLELMONO

B R I D G E - M O N OBridge-Mono mode is used to drive loads with a totalimpedance of at least 4 ohms (see Parallel-Mono if theload is less than 4 ohms). If Bridge-Mono mode and70 volt output are used together, twice the normal out-put voltage is produced from a single channel to drive

Use Dual 70 volt modefor Fire Protective Sig-naling applications (seeSection 9).

Fig. 3.5 Wiring for Dual 70 Volt Mode

+

COM

+

COM

+

+

70 VOLT STEP-DOWNTRANSFORMERS

16, 8, OR 4 OHM

16, 8, OR 4 OHM

70 VOLT LINE

MIXER

LOUDSPEAKERS

Com-Tech Amplifier

CHANNEL 1

CHANNEL 2

CHANNEL 1

CHANNEL 2

DUAL 70 VOLT MODE(BOTH CHANNELS)

TURN OFF THE AMPLIFIERBEFORE CHANGING



OUTPUT MODE SWITCHES.70

VOLT70

VOLT8/4

OHM8/4

OHM

CH1CH2

BRIDGEMONO

DUAL

PARALLELMONO

BB


+C H - 2 I N P U T

+C H - 1 I N P U T

PRESS

R E S E T

PUSH TO RESET

CH-2 CH-10dB

.51

234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32


Fig. 3.6 Wiring for Bridge-Mono 70 Volt Mode (140 Volt Output)

COM

+

+


16, 8, OR 4 OHM

16, 8, OR 4 OHM

140 VOLT LINE

MIXER

LOUDSPEAKERS

Com-Tech Amplifier

CHANNEL 1

BRIDGE-MONO70 VOLT MODE(140 VOLT OUTPUT)




OUTPUT MODE SWITCHES.WARNING: BOTH CHAN-NELS MUST BE SET TO

70 VOLT MODE.

COM

+

+

DO NOTUSE

TURN OFF CHANNEL 2 (CCW)IN BRIDGE-MONO MODE.

DO NOT USETHE GROUNDTERMINALS

BRIDGEMONO

DUAL

PARALLELMONO

BB


+C H - 2 I N P U T

+C H - 1 I N P U T

70VOLT

70VOLT

8/4OHM

8/4OHM

CH1CH2

CH-2 CH-10dB

.51

234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32

PRESS

R E S E T

PUSH TO RESET

minals (see Figure 3.6 and the middle illustration inFigure 3.7). The positive lead from the load connects tothe positive channel 1 terminal, and the negative (orground) lead from the load connects to the positivechannel 2 terminal. Do not connect the outputgrounds ( ). Also, the load must be balanced (neitherside shorted to ground).

CAUTION: Only connect balanced equipment (meters,switches, etc.) to the Bridge-Mono output. Both sides ofthe line must be isolated from the input grounds or os-cillations may occur.

BRIDGEMONO

DUAL

PARALLELMONO

P A R A L L E L - M O N OParallel-Mono mode is used to drive loads with a totalimpedance of less than 4 ohms when using 8/4 ohmoutput mode (see Bridge-Mono if the load is greaterthan 4 ohms). This mode can also be used to drive a

single high-powered 70 volt constant voltage line.

Parallel-Mono installation is very different from theother modes and requires special attention.

WARNING: Both channels must be configured for thesame output mode (8/4 ohm or 70 volt) before switch-ing to Parallel-Mono mode.

To select Parallel-Mono mode, turn off the amplifierand slide the dual/mono switch to the left (as you facethe back panel). Connect the input signal to channel 1only. The channel 2 input jack and level control are by-passed in this mode, so they should not be used.

Note: It is normal for the channel 2 IOC indicator to stayon in Parallel-Mono mode.

Connect the load to the channel 1 output as shown inFigure 3.7 (top and bottom illustrations). The positivelead from the load connects to the positive (+) terminalof channel 1, and the negative (or ground) lead fromthe load connects to the ground ( ) terminal of channel1. Finally, install a jumper wire of at least 14 gauge be-


COM

+

+


16, 8, OR 4 OHM

16, 8, OR 4 OHM

70 VOLT LINE

MIXER

Com-Tech Amplifier

CHANNEL 1

PARALLEL-MONO70 VOLT MODE




OUTPUT MODE SWITCHES.WARNING: BOTH CHAN-

NELS MUST BE SETTO 70 VOLT MODE.

COM

+

+

NOT USED

CHANNEL 2 IS NOT USEDIN PARALLEL-MONO MODE.

BRIDGEMONO

DUAL

PARALLELMONO

BB


+C H - 2 I N P U T

+C H - 1 I N P U T

70VOLT

70VOLT

8/4OHM

8/4OHM

CH1CH2

CH-2 CH-10dB

.51

234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32

PRESS

R E S E T

PUSH TO RESET

LOUDSPEAKERS

ADD A 14 GAUGE ORLARGER JUMPER

BETWEEN THE CHAN-NEL 1 AND 2 POSI-

TIVE (+) TERMINALS.

ADD A 14 GAUGE ORLARGER JUMPER

BETWEEN THE CHAN-NEL 1 AND 2 POSI-

TIVE (+) TERMINALS.

CHANNEL 2 IS NOT USEDIN PARALLEL-MONO MODE.

MIXER

LOUDSPEAKER

Com-Tech Amplifier

CHANNEL 1

PARALLEL-MONO8/4 OHM MODE



+

NOT USED

BRIDGEMONO

DUAL

PARALLELMONO

BB


+C H - 2 I N P U T

+C H - 1 I N P U T

70VOLT

70VOLT

8/4OHM

8/4OHM

CH1CH2



WARNING: BOTH CHAN-NELS MUST BE SETTO 8/4 OHM MODE.

CH-2 CH-10dB

.51

234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32

PRESS

R E S E T

PUSH TO RESET

Fig. 3.7 Wiring for Parallel-Mono 70 Volt, Bridge-Mono 8/4 Ohm and Parallel-Mono 8/4 Ohm Modes

DO NOTUSE

MIXER

LOUDSPEAKER

Com-Tech Amplifier

CHANNEL 1

BRIDGE-MONO8/4 OHM MODE



+

BRIDGEMONO

DUAL

PARALLELMONO

BB


+C H - 2 I N P U T

+C H - 1 I N P U T

70VOLT

70VOLT

8/4OHM

8/4OHM

CH1CH2

TURN OFF CHANNEL 2 (CCW)IN BRIDGE-MONO MODE.

CH-2 CH-10dB

.51

234

56

7891011

1315

17192125

32

0dB.5

1234

56

7891011

1315

17192125

32



WARNING: BOTH CHAN-NELS MUST BE SET TO

8/4 OHM MODE.

PRESS

R E S E T

PUSH TO RESET

DO NOT USE THEOUTPUT GROUND

TERMINALS.


tween the positive (+) terminals of both channels.

CAUTION: When Parallel-Mono wiring is installed, donot attempt to operate in Dual or Bridge-Mono modeuntil the wiring is removed (especially the jumper wire).Failure to do so will result in high distortion and exces-sive heating.

3.3.2 Input ConnectionThe balanced inputs have a nominal impedance of20 K ohms (10 K ohms unbalanced) and will acceptthe line-level output of most devices. The factory-in-stalled P.I.P.-BB provides a balanced three-terminalinput barrier block for each channel (see Figure 2.2).Optional P.I.P. modules like the P.I.P.-FX, P.I.P.-FXQand P.I.P.-FPX can provide female XLR connectors,phone jacks and phono (RCA) connectors. VariousP.I.P.s are also available which provide a wide range

+

INPUT

+

INPUT

2-wire line cord(or battery power)

Note: If two or more channels withthe same input ground reference

are driven from the samefloating source, connect

only one shield to thesource chassis.

Floatingsource

+

3-wire grounded line cord(or other ground connection)

Output

Shield not connectedat this end

Groundedsource

+Output

Fig. 3.9 Balanced Input Wiring

Sometimes large subsonic (subaudible) frequenciesare present in the input signal. These can damageloudspeakers or step-down transformers by overload-ing or overheating them. To attenuate such frequen-cies, place a capacitor in series with the input signalline. The graph in Figure 3.10 shows some capacitorvalues and how they affect frequency response. Useonly low-leakage capacitors.

Another problem to avoid is large levels of radio fre-quencies or RF in the input signal. Although high RFlevels may not pose a threat to the amplifier, they canburn out tweeters or other loads that are sensitive to

of input signal processing features (see Section 8).

Proper input wiring depends on two factors:(1) whether the input signals are balanced or unbal-anced, and (2) whether the signal source floats or hasa ground reference. The following illustrations provideexamples of recommended connection techniques foreach type of signal source.

S O L V I N G I N P U T P R O B L E M S

Fig. 3.8 Unbalanced Input Wiring

+

Twin

-lead

shi

elde

d ca

ble

+

INPUT


Output

Floatingsource

Shield connectedto ground terminal

+

INPUT


Shield not connectedat this end

Groundedsource


Input groundterminal not used

INPUTGrounded

source

Sing

le-c

ondu

ctor

coa

xo

r tw

iste

d pa

ir

+Output

+

INPUT

+


Output

Floatingsource

Shield connected to bothnegative () and groundinput terminals

+Output

+

1 Hz 10 Hz 100 Hz 1 kHz 10 kHz

dB

0

5

10

15

1 f .1 f

.05 f

.01 f

Frequency

Fig. 3.10 Subsonic Filter Capacitor Values


4 kHz 10 kHz 40 kHz 100 kHz

Frequency

dB

0

10

20

A

B

C

6 dB/octave

12 dB/octave

ToAmp

GND

ToAmp

GND

ToAmp

GND

Source

1.8 K

.003f

.015f

.018f

3.9 mH

5 mH

600 Source

R

600 Source

R

A

C

B

Note: A low source impedance (R) can beincreased to 600 by an appropriate resistor.

Fig. 3.11 Unbalanced RFI Filters

high frequencies. Extremely high RF levels can alsocause your amplifier to prematurely activate its protec-tion circuitry, resulting in inefficient operation. RF canbe introduced into a signal by local radio stations and

+

Balanced In

910

.003f

.015f

.018f

1.8 mH

2.5 mH

A

C

B

.015f

1.8 mH

D

Balanced Out

+

910

1.8 mH

2.5 mH

1.8 mH

+

Balanced In Balanced Out

+

+


+

+


+

0.47 Film

0.47 Film

Fig. 3.12 Balanced RFI Filters

from the bias signal of many tape recorders. To pre-vent high levels of input RF, install an appropriate low-pass filter in series with the input signal. Someexamples of unbalanced wiring for low-pass filters areshown in Figure 3.11.

For balanced input wiring, use an example from Figure3.12. Filters A, B, and C correspond to the unbalancedfilters shown in Figure 3.11. Filter D also incorporatesthe subsonic filter in Figure 3.10.

Tip: The standard P.I.P.-BB has plenty of space on itscircuit board for the addition of input filter circuitry.

Another problem to avoid is ground loops. These areundesirable currents that flow in a grounded systemand usually cause hum in the output. A commonsource of ground loop problems is the placement ofinput cables parallel to power cables or near powertransformers. A ground loop can occur when the mag-netic field generated by the 50/60 Hz alternating cur-rent in the power cable or transformer is induced intothe input cables. To prevent this, you can lace the in-put cables along their length. (Lacing cables helps re-duce magnetically induced current by minimizing thecross-sectional area between conductors which couldbisect a magnetic field.) It is also very important to lo-cate input cables away from power cables and trans-formers.

Ground loops often occur when the input and outputgrounds are tied together. DO NOT CONNECT THEINPUT AND OUTPUT GROUNDS TOGETHER. Tyingthe grounds together can also cause feedback oscilla-tion from the load current flowing in the loop. To avoidthis problem, use proper grounding, isolate the inputs,and isolate other common AC devices.

3.3.3 Output ConnectionConsider the power handling capacity of your load be-fore connecting it to the amplifier. Crown is not liablefor damage incurred at any time due to overpowering.Fusing loudspeaker lines is highly recommended (seeSection 3.3.4). Also, please pay close attention to Sec-

Input Wiring Tips1. Use only shielded cable. Cables withhigher density shields are better. Spiralwrapped shield is not recommended.

2. When using unbalanced lines, keep thecables as short as possible. Avoid cablelengths greater than 10 feet (3 meters).

3. Do not run signal cables together withhigh-level wiring such as loudspeaker wiresor AC cords. This reduces the chance ofhum or noise being induced into the inputcables.

4. Turn the entire system off before chang-ing connections. Turn level controls downbefore powering the system back up. Crownis not liable for damage incurred when anytransducer or component is overdriven.


40

30

20

15

10

9

8

7

6

5

4

3

2

1

2

5

10

20

50

100

.04

.06

.1

.2

.4

.6

1

2

4

6

10

20

40

5

10

2050

1

2

100200500

1000

2000

5000

8000

5000

1000

500

100

50

10

5

1

.5

.1

.05

.01

#28#26#24#22#20#18#16#14#12#10#8#6#4#2#0#00#0000

R LOAD

RESISTANCE(ohms)

L

R R

DAMPINGFACTOR

LS

R SOURCE

RESISTANCE(ohms)

S

2-COND.CABLE(feet)

ANNEALEDCOPPER

WIRE(AWG)(ohms/1000 ft.)

Example Shown:R = 8 ohms; R = 0.016 ohms or D.F. = 500;Cable Length = 10 ft.; answer: #8 wire

L S

1

0.5

200

500

1,000

2,000

20,000

5,000

10,000

.01

.001

.02

.004

.006

.002

.0004

.0006

.0002

0.6

0.7

0.8

1.5

0.9

tion 4.1, Precautions.

You should always install loudspeaker cables of suffi-cient gauge (wire thickness) for the length used. Theresistance introduced by inadequate output cableswill reduce the amplifiers power to and motion controlof the loudspeakers. The latter problem occurs be-cause the damping factor decreases as the cable re-sistance increases. This is very important because theamplifiers excellent damping factor can be easily ne-gated by using insufficient cable.

Use the nomograph in Figure 3.13 and the followingprocedure to find the recommended wire gauge (AWGor American Wire Gauge) for your system.

1. Note the load resistance of the loudspeakers con-nected to each channel of the amplifier. If you are using70 volt output, be sure to determine the load resistance ofthe step-down transformers (Crowns constant voltagecomputer can help with this, see Section 8.3). Mark thisvalue on the Load Resistance line of the nomograph.

2. Select an acceptable damping factor and mark it onthe Damping Factor line. Your amplifier can provide anexcellent damping factor of 1,000 from 10 to 400 Hz inStereo mode with an 8 ohm load. In contrast, typicaldamping factors are 50 or lower. Higher damping factorsyield lower distortion and greater motion control over theloudspeakers. A common damping factor for commercialapplications is between 50 and 100. Higher damping fac-tors may be desirable for live sound, but long cablelengths often limit the highest damping factor that can beachieved practically. (Under these circumstances,Crowns IQ System is often used so amplifiers can be eas-ily monitored and controlled when they are located verynear the loudspeakers.) In recording studios and homehi-fi, a damping factor of 500 or more is very desirable.

Use Good Connectors1. To prevent possible short circuits, do notexpose the loudspeaker cable connectors.

2. Do not use connectors that might acciden-tally tie two channels together when making orbreaking connections (for example, a stan-dard three-wire stereo phone plug).

3. Connectors that can be plugged into ACpower receptacles should never be used.

4. Connectors with low current-carrying ca-pacity should not be used.

5. Connectors with any tendency to shortshould never be used.

3. Draw a line through the two points with a pencil, andcontinue until it intersects the Source Resistance line.

4. On the 2-Cond. Cable line, mark the length of thecable run.

5. Draw a pencil line from the mark on the Source Resis-tance line through the mark on the 2-Cond. Cable line,and on to intersect the Annealed Copper Wire line.

6. The required wire gauge for the selected wire length and

Fig. 3.13 Wire Size Nomograph


damping factor is the value on the Annealed Copper Wireline. Note: Wire size increases as the AWG gets smaller.

7. If the size of the cable exceeds what you want to use,(1) find a way to use shorter cables, like using the IQ System,(2) settle for a lower damping factor, or (3) use more thanone cable for each line. Options 1 and 2 will require the sub-stitution of new values for cable length or damping factor inthe nomograph. For option 3, estimate the effective wiregauge by subtracting 3 from the apparent wire gauge everytime the number of conductors of equal gauge is doubled.So, if #10 wire is too large, two #13 wires can be substituted,or four #16 wires can be used for the same effect.

SOLVING OUTPUT PROBLEMSHigh-frequency oscillations can cause your amplifierto prematurely activate its protection circuitry. Theeffects of this problem are similar to the RF problemsdescribed in Section 3.3.2. To prevent high-frequencyoscillations, follow these guidelines:

1. Bundle together each pair of loudspeaker conduc-tors when using long cable runs or when differentamplifiers use a common cable tray or jacket. (DoNOT bundle wires from different amplifiers.) Thisreduces the chance of conductors acting likeantennas to transmit or receive the high frequen-cies that can cause oscillation.

2. Avoid using shielded loudspeaker cable.

3. Never tie together input and output grounds.

4. Never tie together the output of different amplifiers.

5. Keep output cables separated from input cables.

6. Install a low-pass filter in series with each input(see Section 3.3.2).

7. Install the input wiring according to the instructionsin Section 3.3.2.

Another problem to avoid is the presence of large sub-sonic currents when primarily inductive loads areused. Examples of inductive loads are 70 volt trans-formers and electrostatic loudspeakers.

Inductive loads can appear as a short circuit at low fre-quencies. This can cause the amplifier to produce

large low-frequency currents and activate its protec-tion circuitry. Always take the precaution of installing ahigh-pass filter in series with the amplifiers input wheninductive loads are used. A three-pole, 18 dB per oc-tave filter with a 3 dB frequency of 50 Hz is recom-mended (some applications may benefit from an evenhigher 3 dB frequency). Such a filter is described withsubsonic frequency problems in Section 3.3.2.

Another way to protect inductive loads from large low-frequency currents and prevent the amplifier from pre-maturely activating its protective systems is to parallela 590 to 708 F nonpolarized motor start capacitorand a 4 ohm, 20 watt resistor in series with the amplifieroutput and the positive (+) transformer lead. This cir-cuit is shown in Figure 3.14. It uses components thatare available from most electrical supply stores.

3.3.4 Additional Load ProtectionCom-Tech amplifiers can generate enormous poweroutput. Using 8/4 ohm output, if your loudspeakers donot have built-in protection from excessive power, its agood idea to protect them. Loudspeakers are subjectto thermal damage from sustained overpowering and

Fig. 3.15 Loudspeaker Fuse NomographFig. 3.14 Inductive Load (Transformer) Network

4 ohm, 20 wattResistor

590 to 708 f Capacitor120 VAC, N.P.

+

InductiveLoad

+

FromAmplifierOutput

1.0

1.2

1.4

1.6

2.5

3

4

5

6

7

8

9

10

12

14

16

20

25

30

20

15

10

8

6

5

4

3

2

1.5

1

.8

.6

.5

.4

.3

.2

.15

.1

.08

3000

2000

1500

1000800

600

400

300

200

150

10080

60

40

30

20

15

108

6

4

3

2

1.5

1

SPEA

KER

Z(o

hms)

FUSE

(amps

)

SPEA

KER

RATI

NG

PEA

K M

USIC

PO

WER

(watt

s)(T

ypica

lly 4

times

the c

ontin

uous

aver

age p

ower

)

Example: Z = 8 ohms.Peak Power = 75 W

Answer: Fuse = 1.5 A

2

40


mechanical damage from large transient voltages. Inboth cases, special fuses may be used to protect yourloudspeakers, or you may opt for the convenience of aP.I.P. module that provides loudspeaker protection.

Two different types of fuses are required for thermalprotection and voltage protection. Slow-blow fuses areusually selected to protect loudspeakers from thermaldamage because they are similar to loudspeakers inthe way they respond to thermal conditions over time.In contrast, high-speed instrument fuses like theLittlefuse 361000 series are used to protect loud-speakers from large transient voltages. The nomo-graph in Figure 3.15 can be used to select the properlyrated fuse for either type of loudspeaker protection.

There are mainly two different approaches used wheninstalling fuses for loudspeaker protection. A commonpractice is to put a single fuse in series with the outputof each channel. This makes installation easy becausethere is only one fuse per channel to install, but it canalso lead to problems. The biggest disadvantage be-comes apparent if the fuse blows because power to allconnected loads will be removed.

A better approach is to fuse each driver indepen-dently. This allows you to apply the most appropriateprotection for the type of driver being used. In general,low-frequency drivers (woofers) are most susceptibleto thermal damage and high-frequency drivers (tweet-ers) are usually damaged by large transient voltages.

This means that your loudspeakers will tend to havebetter protection when the woofers are protected byslow-blow fuses and high-frequency drivers are pro-tected by high-speed instrument fuses.

Depending on the application, you may want to use aP.I.P. module to protect your loudspeakers. Whenproperly configured, all P.I.P. modules with signal-driven compression can provide loudspeaker protec-tion. Some of the P.I.P. modules with signal-drivencompression include the P.I.P.-AMCb, P.I.P.-EDCband P.I.P.-PA. While the P.I.P.-EDCb is most commonlyused for general loudspeaker protection, the P.I.P.-AMCb is very popular in systems that require a high-quality crossover, and the P.I.P.-PA is the processor ofchoice for applications that require a microphone andline level input for each channel. For more informationon P.I.P. modules, see Section 8.

3.4 AC Mains PowerAll 120 VAC, 60 Hz North American units have a NEMA5-15 AC plug with an integral voltage presence lamp.These units include a 16 gauge cord with Com-Tech200s and 400s, and a 14 gauge cord with Com-Tech800s and 1600s. Other Com-Tech amplifiers are fur-nished with an appropriate AC cord and plug.

Use an isolated wall outlet whenever possible with thecorrect voltage and adequate current. Voltagesgreater than 10% above the specified AC mains volt-age for the amplifier may damage the 15 volt regula-tor, filter capacitors and output transistors. See Section7 for power requirements under various conditions.

All specifications in this manual were measured using120 VAC, 60 Hz power mains unless otherwise noted.Specifications are derived using a mains voltage thatis accurate to within 0.5% with THD less than 1.0% un-der all testing conditions. Performance variations canoccur at other AC voltages and line frequencies. In ad-dition, line regulation problems will directly affect theoutput power available from the amplifier.


4 Operation4.1 PrecautionsAlthough your amplifier is protected from internal andexternal faults, you should still take the following pre-cautions for optimum performance and safety:

1. Improper wiring for the Dual, Bridge-Mono andParallel-Mono modes, as well as the 8/4 ohm and70 volt output modes can result in serious operatingdifficulties. Refer to Section 3.3.1 for details.

2. WARNING: Never attempt to operate the amplifier ineither Bridge-Mono or Parallel-Mono mode unlessboth output channels are configured the same (8/4ohm or 70 volt).

3. When driving an inductive load (like a 70 volt step-down transformer) use a high-pass filter or protec-tive network to prevent premature activation of theamplifiers protection circuitry (see Section 3.3.3).

4. WARNING: Do not change the position of the dual/mono switch or the output mode switches unless theamplifier is first turned off.

5. CAUTION: In Parallel-Mono mode, a jumper mustbe installed between the channel 1 and 2 positive (+)output terminals. Be sure to remove this jumper forDual or Bridge-Mono modes, otherwise high distor-tion and excessive heating will occur. Check thedual/mono switch on the back panel for properposition.

6. Turn off the amplifier and unplug it from the AC mainsbefore removing a P.I.P. card or before removing thedust filter.

7. Use care when making connections, selecting sig-nal sources and controlling the output level. Theload you save may be your own!

8. Do not short the ground lead of an output cable tothe input signal ground. This may form a groundloop and cause oscillations.

9. Operate the amplifier from AC mains of not morethan 10% above or below the selected line voltageand only the specified line frequency.

10. Never connect the output to a power supply output,battery or power main. Such connections may resultin electrical shock.

11. Tampering with the circuitry by unqualified person-nel, or making unauthorized circuit changes may behazardous and invalidates all agency listings.

Remember: Crown is not liable for damage that resultsfrom overdriving other system components.

4.2 IndicatorsThe front panel of a Com-Tech amplifier has severalhelpful indicators. The amber Enable indicator is pro-vided to show the amplifier has been turned on (or en-abled) and that its low-voltage power supply isworking. It does not indicate the status of the high-volt-age power supplies. For example, the Enable indicatorwill remain lit in the unlikely event that one of theamplifiers protection systems (described in Sec-tion 4.3) removes power from one (or both) high-volt-age supplies to put the channel in standby mode.The Enable indicator will be illuminated for all condi-tions shown in Figure 4.1 except for the first example,There is no power to the amplifier.

The green ODEP indicators confirm the normal opera-tion of Crowns patented Output Device Emulation Pro-tection circuitry. During normal operation, they glowbrightly to confirm the presence of reserve thermal-dy-namic energy. They dim proportionally as the energyreserve decreases. In the rare event that there is noreserve, the indicators will turn off and ODEP will pro-portionally limit the drive level of the output stages sothe amplifier can continue safe operation even whenconditions are severe. (For a more detailed descriptionof ODEP, see Section 4.3.1.)

A channels ODEP indicator also turns off if its high-voltage power supply is put in standby mode or theamplifiers circuit breaker is tripped. The standbymode is activated if DC or heavy common-mode cur-rent is detected at the output, if the transformer thermalprotection system is activated, or if a P.I.P. like theP.I.P.-UL1711 or the IQ-P.I.P. is used to shut down ahigh-voltage power supply. (For more information, seeSection 4.3.3 and the table in Figure 4.1.)

The yellow IOC indicators act as sensitive distortionmeters to provide proof of distortion-free performance.The IOC (Input/Output Comparator) circuitry com-pares the incoming signals waveform to that of theoutput. Any difference between the two is distortion.The IOC indicators flash if there is a difference of0.05% or more. It is normal for them to light momen-tarily when the amplifier is first turned on. Note: thechannel 2 IOC indicator will stay on in Parallel-Monomode.

The green Signal Presence Indicators (SPI) flash syn-chronously with the output audio. The SPI detector cir-cuit is connected in the signal path after the input gainstages and level controls, so a flashing indicator tellsyou that there is audio in and out of the amplifier. Note:The Signal Presence Indicators may not report signalpresence if the output signal level is too low.


4.3 Protection SystemsCom-Tech amplifiers provide extensive protection anddiagnostics capabilities. Protection systems includeODEP, standby and an AC circuit breaker. Thesefeatures provide protection under any conditions.

4.3.1 ODEPCrown invented ODEP to solve two long-standingproblems in amplifier design: to prevent amplifier shut-down during demanding operation, and to increasethe efficiency of the output circuitry.

To do this, Crown established a rigorous program tomeasure the safe operating area (SOA) of each outputdevice before installing it in an amplifier. Next, Crowndesigned intelligent circuitry to simulate the instanta-neous operating conditions of the output devices. Itsname describes what it does: Output Device Emula-tion Protection or ODEP. In addition to simulating theoperating conditions of the output devices, it also com-pares their operation to their known SOA. If ODEP seesthat more power is about to be asked of the output de-vices than they are capable of delivering under the

OFFOFFOFF

There is no power to the amplifier. Possible reasons: (1) The amplifiers Enable switch is off. (2) Theamplifier is not plugged into the power receptacle. (3) The AC mains circuit breaker has been tripped.(4) The amplifiers back panel circuit breaker has been tripped. (5) The amplifiers low-voltage powersupply fuse has blown.

Indicator Status Amplifier Condition

Normal operation for a channel with NO output. Possible reasons: (1) There is no input signal.(2) The channels level control is turned down.

Normal operation with an input signal. The signal presence indicator (SPI) will flash to show thatan audio signal is present.

The channels output is exceeding 0.05% distortion. The input signal level is too high, and IOCis reporting either an input overload or output clipping.

No output: The amplifier channel is in standby mode. Possible reasons: (1) The DC/low-frequencyprotection circuitry has been activated. (2) The fault protection circuitry has been activated after sensingheavy common-mode current. (3) The transformer thermal protection circuitry has been activated.

ODEP limiting has been activated. Possible reasons: (1) The amplifiers air filters are blocked andneed to be cleaned. (2) There is insufficient cooling because of inadequate air flow or air that is too hot.(3) The load impedance for the channel is too low because the output is shorted or the amplifier isdriving too many loudspeakers for the selected dual/mono mode. (4) The amplifier channel iscontinuously being driven to very high output levels.

ODEP limiting is about to begin. Possible reasons: (1) The amplifiers air filters are blocked and needto be cleaned. (2) There is insufficient cooling because of inadequate air flow or air that is too hot.(3) The load impedance for the channel is too low because the output is shorted or the amplifier isdriving too many loudspeakers for the selected dual/mono mode. (4) The amplifier channel iscontinuously being driven to very high output levels.

ODEP

IOC

SPI

ONOFFOFF

ODEP

IOC

SPI

ONOFFActive

ODEP

IOC

SPI

ONONActive

ODEP

IOC

SPI

ONONOFF

ODEP

IOC

SPI

OFFOFFActive

ODEP

IOC

SPI

Channel 2 only: The amplifier is in Parallel-Mono mode and has output. The channel 2 IOCindicator always turns on when the amplifiers dual/mono switch is moved to the Parallel-Mono position.

No output: The amplifier channel is in standby mode. Possible reasons: (1) The amplifier has justbeen turned on and is still in the four second turn-on delay. (2) A P.I.P. module such as an IQ-P.I.P.or the P.I.P.-UL1711 has turned off the channels high-voltage supply.

OFFONOFF

ODEP

IOC

SPI

OFFONActive

ODEP

IOC

SPI

OR

Channel 2 only: The amplifier is in Parallel-Mono mode with no output. The channel 2 IOCindicator always turns on when the amplifiers dual/mono switch is moved to the Parallel-Mono position.

OR

Fig. 4.1 ODEP, IOC and Signal Presence Indicator States


present conditions, ODEP immediately limits the drivelevel until it falls within the SOA. Limiting is proportionaland kept to an absolute minimumonly what is re-quired to prevent output device damage.

This level of protection enables Crown to increase out-put efficiency to never-before-achieved levels whilegreatly increasing amplifier reliability.

The on-board intelligence is monitored in two ways.First, the front panel ODEP indicators show whetherthe amplifier is functioning correctly or if ODEP is limit-ing the drive level. Second, ODEP data is fed to theconnector inside the amplifiers back panel P.I.P. com-partment so advanced P.I.P. modules like the IQ-P.I.P.can use it to monitor and control the amplifier.

This is how ODEP keeps the show going with maxi-mum power and maximum protection at all times.

4.3.2 Standby ModeAn important part of a Com-Tech amplifiers protectionsystems is standby mode. Standby protects the ampli-fier during potentially catastrophic conditions. It tem-porarily removes power from the high-voltage suppliesto protect the amplifier and its loads. Standby modecan be identified using the indicator table in Fig-ure 4.1.

When you turn on the Enable switch, standby mode isactivated to provide turn-on protection. This power-updelay lets other system components settle before anysignals are amplified, and it provides some random-ness to the power-up sequence of multiple units whichreduces the systems current demand during start-up.

If dangerous subsonic frequencies or direct current(DC) is detected in the amplifiers output, the unit willactivate its DC/low-frequency protection circuitry andput the affected channels in standby. This protects theloads and prevents oscillations. The unit resumes nor-mal operation as soon as the amplifier no longer de-tects dangerous low-frequency or DC output. Althoughit is extremely unlikely that you will ever activate theamplifiers DC/ low-frequency protection system, im-proper source materials such as subsonic squarewaves or input overloads that result in excessivelyclipped input signals can activate this system.

The amplifiers fault protection system will put an ampli-fier channel into standby mode in rare situations whereheavy common-mode current is detected in achannels output. The amplifier should never outputheavy common-mode current unless its circuitry isdamaged in some way, and putting the channel in

standby mode helps to prevent further damage.

The amplifiers transformer thermal protection circuitryis activated in very unusual circumstances where theunits transformer temperature rises to unsafe levels.Under these abnormal conditions, the amplifier will putboth channels into standby mode. In addition, thecooling fan will run at full speed. The amplifier will re-turn to normal operation after the transformer cools to asafe temperature. (For more information on trans-former thermal protection, refer to the section that fol-lows.)

4.3.3 Transformer Thermal ProtectionAll Com-Tech amplifiers have transformer thermal pro-tection which protects the power supplies from dam-age under rare conditions where the transformertemperature rises too high. A thermal switch embed-ded in the power transformer removes power to thehigh-voltage power supplies if it detects excessiveheat. The switch automatically resets itself as soon asthe transformer cools to a safe temperature.

If your amplifier is operated within rated conditions, it isextremely unlikely that you will ever see it activatetransformer thermal protection. One reason is thatODEP keeps the amplifier working under very severeconditions. Even so, higher than rated output levels,excessively low-impedance loads and unreasonablyhigh input signals can generate more heat in the trans-former than in the output devices. This can overheatthe transformer and activate its protection system.

Com-Tech amplifiers are designed to keep workingunder conditions where other amplifiers would fail. Buteven when the limits of a Com-Tech are exceeded, it stillprotects itselfand your investmentfrom damage.

4.3.4 Circuit BreakerA circuit breaker is provided to prevent excessive cur-rent draw by the high-voltage power supplies. A resetswitch for the circuit breaker is provided on the backpanel. The rating of the circuit breaker for each ampli-fier model and each AC mains voltage is provided withthe specifications in Section 6. When operating withrated loads and output levels, this breaker should onlytrip in the incredibly rare instance of a catastrophicamplifier failure. Other protection systems such asODEP keep the amplifier safe and operational undermost other severe conditions. The breaker can alsotrip in situations where extremely low-impedanceloads and high output levels result in current draw thatexceeds the breakers rating. Again, this should onlybe possible when operating outside rated conditions,


like when the amplifier is used to drive a 1 ohm load, orwhen an input signal is clipped severely.

4.4 ControlsThe Enable switch is located on the front panel so youcan easily turn the amplifier on and off. If you everneed to make any wiring or installation changes, dontforget to disconnect the power cord. Please followthese steps when first turning on your amplifier:

1. Turn down the level of your audio source. Forexample, set your mixers volume to .

2. Turn down the level controls of the amplifier.

3. Turn on the Enable switch. The Enable indicatorbeside the switch should glow. During the foursecond turn-on delay which immediately follows,the indicators will flash as described in Figure 4.1.After the delay, the ODEP indicators should comeon with full brilliance and the IOC and SignalPresence Indicators should function normally.

4. After the turn-on delay, turn up the level of youraudio source to the maximum desired level.

5. Turn up the level controls on the back panel of theamplifier until the maximum desired loudness orpower level is achieved.

6. Turn down the level of your audio source to itsnormal range.

A 22-position detented level control is provided foreach channel. For security, the level controls are lo-cated on the back panel. To prevent tampering fromthe rear, a Lexan cover is provided that can be at-tached to the back panel with the included 12" 8-32screws.

Com-Tech amplifiers have a back panel reset switchfor the AC mains circuit breaker. If the circuit breakertrips for some reason, the Enable indicator will turn off.In this situation, turn off the Enable switch and reset thecircuit breaker. Then turn the Enable switch back on. Ifthe breaker trips again or if the unit fails to operateproperly, contact an authorized service center orCrowns Technical Support Group.

A three-position input sensitivity switch is located in-side the amplifiers P.I.P. compartment. It is set at thefactory to a sensitivity of 0.775 volts (8/4 ohm mode).Please notice that there is a separat

Crown Com Tech 400 Owners Manual

Documents

Transcript of Crown Com Tech 400 Owners Manual