The equaliser shall provide ±12dB of boost and cut at30 1/3 octave ISO centre frequencies from 25Hz-20kHz, selectable to ±6dB for increased faderresolution.

The equaliser shall meet or exceed the followingperformance specifications:

Frequency Response ± 0.5dB (20Hz-20kHz)Distortion (THD+N) <0.003% @1kHz, +4dBuDynamic Range >114 dB (20Hz-20kHz unweighted,±12 dB range)

The equaliser shall allow have one adjustable second-order low pass filter and one adjustable second-orderhigh pass filter per channel, and two adjustableoverlapping notch filters per channel.

The unit shall have an equalisation section by-passand shall be fail-safe, that is the unit shall returnautomatically to the by-pass condition in the event ofpower supply interruption.

Each equaliser shall use centre-detented slidepotentiometers arranged to give a graphical display offrequency plotted against level. The slidepotentiometers shall have protective covers to inhibitthe ingress of dirt and dust.

All audio connections shall be electronically balancedand use XLR and Phoenix style connectors. Input andoutput transformers shall be available as an option.

The unit shall be capable of operating from a 100-240V ± 10% 50/60Hz a.c. power source.

The equaliser shall be the Klark Teknik Dual Channelmodel DN370, and no alternative specification optionis available.

Technical Specification

Input Two

Type Electronically balanced (pin 2 hot)

Impedance (Ω) 20kMaximum input level +22dBu

Outputs TwoType Electronically balanced

(pin 2 hot)Minimum load impedance 600 ΩSource impedance <60 ΩMaximum output level +22dBu into >2kΩ

PerformanceFrequency response ±0.5 dBu 20Hz-20kHz

relative to signal at 1kHzEQ out ±0.5 dBuEQ in (flat) ±0.5 dBuDistortion (THD+N) < 0.003% @ 1kHz, +4 dBuDynamic range >114dB (20Hz-20kHz

unweighted, ±12dB range)Overload indicator +20 dBuGain - ∞ to +6dBu

Equalisation 30 BandsCentre Frequencies To BS EN ISO 266:1997

25Hz-20kHz, 1/3 octaveTolerance ±5%Maximum Boost/Cut ±12dB, ±6dBHigh Pass Filter Slope 12 dB/octaveLow Pass Filter Slope 12 dB/octaveNotch filter attenuation >17dB, Q=32

TerminationsAudio 3-pin XLR and

6-pin PhoenixPower 3-pin IEC

Power RequirementsVoltage 100V-240V a.c.Consumption <60W

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Architect’s & Engineer’s Specification

DN370: Graphic Evolution

DimensionsHeight 133mm (5.25 inch)

(3U High)Width 482mm (19 inch)Depth 205mm (8 inch)

WeightNett 5.8kgShipping 7.0kg

OptionsInput and output balancing transformers

Trade Descriptions Act:Due to the company policy of continuing improvement, we reserve theright to alter these specifications without prior notice. E&OE.

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Klark Teknik Group, Walter Nash Road, Kidderminster,Worcestershire, DY11 7HJ. England.Tel: +44 1562 741515 Fax: +44 1562 745371email: sales@ktgplc.com www.klarkteknik.com

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INTRODUCTION:

The all-new Klark Teknik DN370 is the latest evolutionarystep in a process of design refinement that goes backover 30 years. With DN370 we’ve started from the groundup and produced a unit that is totally withoutcompromise, and one that we believe is the finestprofessional graphic equaliser in the world today. It alsoperfectly complements the existing Klark Teknik range ofequalisers, both analogue and digital.

Our aim is simply to provide discerning professionalusers with the best possible solutions for system control.Our market research shows that the graphic equaliser isstill the most commonly-used EQ device in fixed andmobile live sound applications, as well as manyinstallations, mainly because the physical user interfaceprovides instant access and controllability in even themost demanding environments. To this end we havecompletely re-evaluated the role of the graphic EQ,focusing exclusively on providing a new feature set thatbetter reflects the needs of modern users.

Like all Klark Teknik units, DN370 is engineered for alifetime of hard use and carries our 3-year internationalfactory warranty.

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Signal present/clip Gain High pass filter Low pass filter

Notch filtersEQ in/outRange

I/O:

The DN370 has electronically-balanced input and outputcircuits to preserve the highest signal integrity. Theinputs have excellent common-mode rejection and theoutputs have high-drive capability to cope with longcable runs. Although equalisers are more generally usedon console inserts, the DN370 is fully capable of beingused in-line with cables running the long distancesbetween the Front Of House mix position, the main stageand the delay towers in festival PA systems. Transformerbalancing is available as an additional option on both theinputs and outputs.

DESIGN:

The most important design decision for the DN370 wasdetermining the equaliser response. Proportional-Qequalisation, as used on previous Klark Teknik analoguegraphic equalisers, offers some key advantages over themore numerous Symmetrical-Q equalisers on the market,namely at low amounts of cut or boost the width of thefilter is relatively broad and becomes narrower as theamount of boost or cut is increased, giving a more'focused' response. This differs from a Symmetrical-Qresponse, which boosts or cuts an increasingly wide bandof frequencies, as more of the frequency spectrum is lostwhen using Symmetrical-Q.

BUILD:

The choice of passive components is critical to ensuringcircuit stability and performance. Premium componentswere chosen to eliminate the non-linear characteristicsfound in other designs, and to achieve the sonic purityfor which Klark Teknik is renowned.

Whilst retaining its traditional values, Klark Teknik usesstate of the art PCB layout and manufacturingtechniques, combined with the use of the latest surfacemount components to produce the DN370. These newtechniques have made it possible to fit the filter circuitsto rear of the fader PCB, with each filter circuit fittingwithin the footprint of its associated fader. Thisminimises the length of connections from each fader toits filter circuit, reducing susceptibility to RFI to aminimum and maximises stability.

45mm faders

DN370: Dual channel 30 band graphic equaliser

FEATURES:

Long-throw 45mm oil-damped faders with dust coverfor increased accuracy and resolution.

All-new proportional-Q filters provide optimum controlwithout undesirable audio artifacts.

Gain control with +6dB/-infinity range and centredetent at unity gain. Allows effective muting of channelin emergencies.

Range switch selects ±6dB or ±12dB operation for thefaders, with LED indication.

Channel bypass switch with LED indication – the unitalso provides automatic relay bypass in the event ofpower failure.

Sweepable high-pass filter with 20Hz to 500Hz range –sets the lower frequency limit of the system. Thecontrol incorporates a push switch to select the filter inand out, with an illuminated ring for “at a glance” statusindication. Invaluable for smooth rejection of unwantedsubsonic and low frequencies, particularly relevant withmodern, compact wedge monitors.

Sweepable low-pass filter with 2kHz to 20kHz range –sets the upper frequency limit of the system. Thecontrol incorporates a push switch to select the filter inand out, with an illuminated ring for “at a glance” statusindication. Provides optimum bandwidth control forvocal monitors and IEM systems.

Two sweepable notch filters per channel, withoverlapping frequency ranges of 20Hz to 2kHz and200Hz to 20kHz. These allow precise removal ofproblem frequencies with minimal effect on the rest ofthe program material, and fast control of “betweenfader” frequencies. This gives precise control of roomand loudspeaker resonance/feedback nodes withminimum loss of energy – even between ISO centres.The controls each incorporate a push switch to selectthe filter in and out, with an illuminated ring for “at aglance” status indication.

Bypass switch with status LEDs for quick comparison ofapplied EQ.

Power switch, fully recessed in the “on” position to avoidaccidental operation.

Signal present LEDs show the presence of audio signalsabove –40dBu.

Multi point clip monitoring. Clip warning LEDsilluminate when the level exceeds +20dBu (2dB belowthe onset of clipping) to assist in optimum system gainsetting.

Electronically balanced inputs and outputs (transformerbalancing is available as an option). Connections areprovided on both XLRs (pin 2 hot) and Phoenix-typestrip connectors for fixed installation.

IEC mains inlet. The unit automatically adjusts foroperation on all voltages from 100 to 240V AC.

KT logo for quality engineering and reliability.

3-year KT warranty for peace of mind.

Rugged, roadworthy steel chassis.

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The notch filters on the DN370 can be used to eliminate a common problem with graphic equalisers - thecontrol of frequencies that lie between the ISO standard frequency centres. In the adjacent example tocut 900 Hz, a single notch filter can be used to produce a steep notch in the frequency response withoutaffecting adjacent frequencies (shown in red). In contrast with a Symmetrical-Q equaliser, the onlysolution available is to cut both the 800 Hz and 1 kHz faders, and whilst there is nearly 16 dB ofattenuation at 900 Hz, a very broad range of frequencies are also affected, particularly when aSymmetrical-Q equaliser with a wide response is used (shown in green). A narrow Symmetrical-Qresponse affects a less broad range of frequencies, although at the expense of less attenuation at thedesired frequency (shown in brown).

The proportional-Q response of the DN370 simultaneously allows gentle contouring of the frequencyspectrum and precise control of specific problem frequencies. The sweepable notch filters furtherenhance this capability. The blue trace shows a high shelf filter created using the faders from 2.5 kHzupwards, and a notch created by fully cutting the 800 Hz fader (Channel A on the front panel view). Thered trace shows the same shelf filter response, but using a notch filter to cut 800 Hz, showing the greaterprecision offered by the notch filters (Channel B on the front panel view).

In contrast, the limitation of Symmetrical-Q equalisers can be seen in the adjacent traces - a wideresponse (shown in green) gives a smooth shelf filter but affects a very broad range of frequencies whenattempting to use it as a notch filter, whilst a narrow response (shown in brown) gives a much sharpernotch, but at the expense of excessive ripple in the shelf filter. Even with a narrow response, theSymmetrical-Q equaliser affects a broader range of frequencies than using the Proportional-Q responseof the DN370’s faders.

The ability to overlap the notch filters, both with each other and with the graphic EQ bands, allows verydeep notches to be created. The adjacent trace shows the responses of a single notch filter, twooverlapped notch filters (both shown in blue) and two notch filters overlapped with an EQ band (shownin red), each resulting in greater attenuation. Nearly 45 dB of attenuation is possible when using thenotch filters in conjunction with the EQ bands.

A typical application of DN370 would be to EQ a monitor wedge, the red trace shows how both the highand low pass filters have been used to shape the overall response, and the use of the two notch filters toattenuate particular problem frequencies. Note that the faders are completely flat, and so can be used tomake incremental changes relative to the response shown above. In contrast, a Symmetrical-Q equalisereven with a high pass filter cannot produce the same response, either with a wide or narrow response(green and brown traces). The effect of the interaction caused by combining the individual faderresponses makes it impossible to match the response created using the DN370’s filters, and whilst thenarrow response is more able to produce the desired notches, it is again at the expense of ripple in thelow pass filter response.

A Symmetrical-Q equaliser lacking the additional filters cannot produce a high pass filter response usingjust its faders, either with a wide or narrow response (green and brown traces). The user may assume thatsubsonic frequencies are being attenuated by cutting the bottom faders but the graph shows that this isnot the case.

APPLICATIONS:Front-of-houseThe all-new graphic EQ filters of the DN370 have beencarefully selected to allow subtle tonal correction with aminimum of ripple between adjacent bands. At the sametime, the proportional-Q nature of the filters ensures thatin the event of acoustic feedback a tightly-focussed cutresponse is instantly available just by moving the fader.Range switching between ± 12dB or ± 6dB, togetherwith 45mm long-throw faders provides superb controlresolution and excellent visibility of control settings. Thesweepable high and low-pass filters allow the frequencyextremes to be matched to the capabilities of theloudspeaker system in use, leaving all the graphic EQfaders available for acoustic management of the music.Twin sweepable notch filters provide excellentsuppression of room resonances with minimum impacton the program material. Positive in/out switching for allthe filter sections is combined with illuminated ringsaround the controls for instant “at a glance” statusindication.

MonitorsThe design of the all-new graphic filters with carefullyselected proportional-Q responses ensures that problemfrequencies can be attenuated quickly and effectively.Long-throw faders allow excellent control resolutioneven when using all of the available 12dB of attenuation.Interaction with adjacent bands is minimised, ensuringthat more of the musical content is preserved. Evenmore precise are the two sweepable notch filters on eachchannel, which allow the surgical removal of resonancesand feedback leaving everything else intact. Pushswitches incorporated in the control knobs allow thefilters to be switched easily in and out (for example whenan artist is using different instruments during a show).Illuminated rings around the control knobs ensure thatthe filter status is always visible at a glance. High andlow-pass filters allow the frequency limits to beaccurately controlled for each output. Whilst very usefulfor conventional wedge monitors, this feature reallycomes into its own when combining in-ear and wedgemonitors, allowing the response of each monitor sub-system to be tailored to the artist’s requirements.

ExamplesThe additional versatility offered by the DN370’s uniquefeature set of filters allows unparalleled precise control offrequency response. The examples adjacent show howthe filters can be used on their own and in conjunctionwith the graphic equaliser to handle problemsencountered in real world corrective EQ applications.

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