Klark Teknik DN27A User manual

DN27A
OPERATORS
MANUAL
KMRK-TEKniK
RESERRCH LimiTED
Kidderminster Worcestershire England
Telephone [phone] Telex 339821

CONTENTS
INTRODUCTION
FUNCTIONS EXPLAINED
CONNECTIONS
TECHNICAL SPECIFICATIONS
CIRCUIT DIAGRAMS
WARRANTY

INTRODUCTION
The Klark-Teknik DN27A 1/3rd Octave Graphic Equalisi
is the successor of the widely acclaimed DN27. It
atotally professional unit which combines the ease
use and reliability of its predecessor with many nei
features and improvements, to give uncompromising
performance and maximum possible flexibility.
Considerable experience in the field of equalisatioi
coupled with aphilosophy of continual research and
development, has enabled the realisation of aprodui
which meets the design criterion; simply the best.
Use of the highest quality materials and components
maintained throughout: Precision -ground air-gap
ferrite cores and custom-wound coils are combined ti
produce the inductors required in each filter; the
faders are oil-damped for smooth, positive operatioi
The construction is completely dependable and robus
every unit being thoroughly tested both electronics
and subjectively before leaving the factory.
The new DN27A features delayed turn-on, "equaliser"
and "total system" bypass, an earth-lift facility,
plug-in p.c.b options.
Operated according to this manual the DN27A should i
years of trouble-free service.
INOTE IThis manual does not include servicim
*information. Any maintenance or repa
should be carried out by aqualified
engineer
.

FIG1

CONTROL CONNECTOR& INDICATOR FUNCTIONS
(1) Power on/off is by atwo-pole toggle switch
(which disconnects live and neutral lines whei
off ).
(2) Power status is indicated by ared led.
(3) The input level control facilitates input-
output system gain of up to 6dR when fully
clockwise, and full attentuation of input sigi
when anti-clockwise,
(4) For instant A-B comparison between dry and
equalised output an "eg" bypass switch is
provided.
(5) Each fader has atravel length of 60mm giving
high resolution of settings, and acentre deti
allowing accurate "flat" or OdB setting.
(6) Mains inlet is via an lEC standard 3-pin sock(
(see page 7)
.
(7) Aseparate holder contains the main fuse.
(8) An earth lift switch is provided on the rear
panel (see notes on page 6).
(9) &(10) Input and output connections are made v
complementary 3-pin XLR sockets situated on tl
rear panel (see page 8).
(11) The serial number this label should be quo

OTHER FEATURES
In addition to the functions previously mentioned, the
DN27A has several note-worthy features.
The main p.c.b houses arelay and associated drive
network which performs two important functions.
1) The output socket is isolated from the equaliser
until power is switched on and all internal power rail
are stable. This "delayed turn-on" prevents D.C. or
transients caused by powering-up from being transmitte
to successive pieces of equipment;
2) If, during operation, aloss of power to or power
related failure in the DN27A should occur, the input i
electronically connected directly to the output, provi
"total system bypass". Subsequently, loss of power do
not cause complete loss of signal; this may save
considerable problems in a"live" situation.
The DN27A power supply includes output voltage regulat
which are designed to shut-down if over-heated and are
current-limiting. The supply rails are of higher volt
than used in previous units, and allow an output clipp
level of +23dBm as well as an extremely good dynamic r
Also provided on the main p.c.b is a12 terminal conne
(via which input and output lines travel) permitting e
addition of line balancing on an optional plug in boar
Power rails are also present on this connector achievi
maximum flexibility, i.e. aplug-in p.c.b could house
transformer and/or electronic balancing, and could als
include such facilities as active filters. (When no s
option is used adummy p.c.b is plugged-in to complete
input and output lines.)
As mentioned earlier, an earth-lift switch is situated
on the rear panel. Activating this switch connects/
disconnects signal gound to/from the mains and chassis
earth. Use of this feature mav Drove invaluable if

CONNECTIONS
(1)Mains
Connection by an lEC standard power socket
nominal mains voltage required by the unit
indicated by alabel underneath the inlet !
If the unit is to be used with any other m<
voltage, selection is internally switchablf
[NOTE I
Any alteration of voltage self
should be made by aqualified
Before connecting the DN27A tt
power ensure that the correct
CAUTION Ifuse is fitted. Under no cirf
should any fuse other than thi
type be used.
Iwarning] The DN27A is fitted with a3-|
For safety reasons the earth t

(2)INPUT
Permissible input level is virtually unlimited due to
the input attenuator, and A.C. coupling affords input
protection from problems caused by D.C. offsets. The
input impedance is nominally 10K ohms at any gain
setting
.
Output drive capability is +23dBm into a600 ohms load.
The input and output specifications make the DN27A readily
compatible with the best professional quality equipment.
One point regarding signal levels should however, be made.
High level input signals should be attenuated sufficiently
to allow gain in the equaliser section without exceeding
the output clipping level. Transients should also be
considered and adequate level headroom be allowed to
process these accurately.

SPECIFICATIONS
Filters :
Centre Frequency Accuracy :
Calibration Accuracy :
Frequency Response :
Output Clipping Point :
Distortion :
Equivalent Input Noise ;
Dynamic Range :
Input Impedance ;
Output Source Impedance :
Bypass :
Power Requirements :
Dimensions :
Optional Accessories :
27 filters with centres at 40
50,63,80,100,125,160,200,250,
315,400,500,630,800,1K,1 .25K,
1.6K,2K,2.5K,3.15K,4K,5K,6.3K
8K,10K,12.5K,16KHz.
Better than t2?^ of nominal.
t0.5dB.
t0.5dB,20-20KHz with controls
flat
+23dBm (11V) into 600 ohm load
Less than 0.01?o IKHz at +4dBm
into 600 ohm load. Less than
0.05?i 20Hz-20KHz at +18dBm
into 600 ohm load.
Less than -95dBm 20Hz-20KHz
unweighted
.
Greater than 115dB
10K ohms nominal
56 ohms short circuit protect
Equaliser bypass via front pa
control .System bypass via gol
contact relay during "power
down" or when unit is switche
off.
200-240V A.C. (100-120V inter
switchable) 50-60Hz at 5VA.
Width 482 mm(l9")
Height 137 mm(5.4")
Depth 212 mm(8.4")
Input and output balancing
transformers; Perspex securit
covers; Teak veneered case;
Heavy-duty wooden case.
27 slide controls for equaliser filters
By-pass switch
Level control
Power switch with L.E.D. indicator
Earth lift (on rear panel)

Circuit Board &Mechanical Layout
1Preset potentiometer VR20 Adjusted for unity gain with panel level control
VR 29 at mid position
2Voltage selector SW2 set for iiov or (220v) nominal.
Disconnect MAINS before changing
3Dimensions shown below include dust cover sleeve. Panel height is to
mount in standard G.P.O. rai