DDA Klark Teknik, cs8 User Manual

CS8

Service Manual

Klark Teknik Building

Walter Nash Road

Kidderminster

Worcestershire

DY11 7HJ

Tel: [phone]

Fax: [phone]

Email: [e-mail]

Website: www.ddaconsoles.com

CS8 Service Manual

 Telex Communications (UK) Limited

In line with the company’s policy of continual improvement, specifications and function maybe subject

to change without notice. This Operator Manual was correct at the time of writing. E&OE.

2

Contents

INTRODUCTION ......................................................................................... 4

CS8 SPECIFICA TIONS ................................................................................. 9

OPTIONS ...................................................................................................... 9

CS8 DIMENSIONS AND WEIGHTS ........................................................ 10

DECLARA TION OF CONFORMITY ........................................................ 11

INST ALLA TION GUIDE............................................................................. 12

ATTENTION ............................................................................................... 13

CIRCUIT DESCRIPTIONS .......................................................................... 14

INPUT MODULE (CD1279) ..................................................................... 1 4

INPUT MODULE LINKS ........................................................................... 19

INPUT MODULE BLOCK DIAGRAM ..................................................... 20

THE STEREO INPUT MODULE (CD1302/3).......................................... 21

STEREO INPUT LINKS .............................................................................. 25

STEREO INPUT MODULE BLOCK DIAGRAM ..................................... 26

THE GROUP OUTPUTS (CD1280/CD1286) .......................................... 2 7

GROUP OUTPUT LINKS (MA TRIX)........................................................ 31

GROUP OUTPUT LINKS (RETURN) ....................................................... 32

GROUP OUTPUTS 1-6 BLOCK DIAGRAM ........................................... 33

GROUP OUTPUTS 7-8 BLOCK DIAGRAM ........................................... 34

THE MASTER MODULE........................................................................... 35

MASTER MODULE LINKS ....................................................................... 39

MASTER MODULE BLOCK DIAGRAM................................................. 41

THE BUS LINKING PORT......................................................................... 42

THE METERBRIDGE ................................................................................. 43

THE POWER SUPPL Y ............................................................................... 45

BUS CONNECTOR PIN OUT ................................................................... 47

CS8 MA TRIX CONNECTO R ..................................................................... 48

BUS LINK CONNECTOR .......................................................................... 49

CS8 P AR TS LISTING .................................................................................. 50

SER VICE INFORMA TION ......................................................................... 58

CS8 CIRCUIT DIAGRAMS ........................................................................ 60

The information in this manual has been carefully verified and is believed to be
correct, however, EVI Pro Audio reserves the right to modify the product
described in this manual at any time. This document may not be copied or
reproduced by any method whatsoever, whether in part or in whole, without
the written permission of EVI Pro Audio.

© Copyright 1997 EVI Pro Audio Group. All rights reserved.

Manual Version DOC03-CS12M/A.

3

INTRODUCTION

The CS8 console has been designed to provide the consultant,
contractor, installer and user with a cost effective system which
will perform to accepted professional standards, be simple for the
untrained user to operate, and be tolerant of wiring and installation
problems. There can be no excuse for a system which is over sensitive
to the wiring and installation conventions used, and hums at every
opportunity.

High quality balanced inputs and outputs are only part of the story.
Equally important is the way in which the console grounding system
works, because it is through the console ground that all the noisy
ground currents from the cable screens will flow. Any part of the
audio signal path which shares the cable screen to console ground
path within the console will effectively have the cable screen noise
added to that signal path. The current flowing in cable shields in
typical installations has be shown to be substantial (in the order of
100mA and above) and is caused by the difference in potential
between the ground connection at each end of the cable screens.

Of comparable importance to any system performance is the power
supply. Internal linear power supplies may be less expensive, but
are usually responsible for inducing noise into the audio and
generating substantial amounts of heat, making it uncomfortable
for the operator. Internal switch mode supplies may be cool running,
but are usually even more of a problem with regard to noise.
Another often overlooked point with internal power supplies is
how to provide auto-switchover between 2 supplies without
extensive modification thereby nullifying the warranty. Internal
supplies are also a potential problem from a maintenance point of
view.

Most service technicians can easily fault find and repair a linear
supply with commonly found components, but a switch mode supply
does not make use of common off the shelf components. Although
more expensive, a separate and generously rated linear power
supply is used with the CS8 keeping heat and noise away from the
console. Rack mounting ears are available for permanent
installations, and the supply is UL and CSA approved.

At this point it is useful to look at some of the features of the CS8.

PAN AND ROUTING
The pan pot can be switched between stereo panning mode, and
left/centre/right panning mode. Left-centre-right panning to the
master outputs provides much improved spatial positioning. The
technique has been used for many years in the film industry where
its benefits are well known.

4

In music systems the centre channel generates a more solid centre
image, especially for the “star” of the show, and helps to maintain
a stereo image across a wider sound stage. In mixed media
productions and in church applications the use of a speech optimised
centre cluster can improve intelligibility without compromising the
music system performance.

If only a stereo system is being run, and the pan pot is switched to
stereo mode, then the centre output is individually assignable from
each input or the from a sum of the left/right mix to provide a
separate mono output for broadcast/film feeds etc.

Another unique feature for a mixer in this class is individual sub
group routing instead of the inconvenient and inflexible paired
routing which always requires the use of the pan pot to route a
channel to a single sub group. There is always a crosstalk
performance compromise involved and it is done solely for economic
rather than for operational reasons, as it halves the number of
routing switches and removes the need for a pan in/out switch.
The CS8 allows routing to the sub groups either individually or in
pairs via the pan pot.

EQUALISATION
The CS8 input module has a 4 band equaliser with high and low
frequency boost/cut controls and two swept frequency middle
sections. There is more than two octaves of overlap between the
frequency ranges of the mid equalisers while the frequency span
extends to from 70Hz to 10kHz.

AUXILIARIES
The CS8 has 8 full time auxiliary send controls allowing easy session
setup. These are normally post fade but can be switched pre fade.
Normally the pre fade signal is pre fade post cut but byusing internal
links it can be changed to the pre equaliser signal. Auxiliaries 7 and
8 can be used in stereo where stereo foldback, for example, is
required.

CHANNEL CUT
The channel cut is a silent FET switch which can be remotely
controlled through a connector on the rear of each channel by a
simple connection to ground. In addition, when the channel cut
switch is pressed, another contact is grounded on the Mute Remote
connector. This can be used to control a Midi Mute controller, cue
lights, or even to control another channel on the mixer by linking
the mute out pin of one channel to the mute in pin of any other
channel(s). Such an application could be a podium switch which
would allow the speaker to override other channels for example.

5

SOLO/PFL MONITORING
While it is normal to find PFL/AFL on almost all mixers, the CS8
goes a step further. The input solo is arranged to have priority over
the output solo. This means that there is no need to de-select an
output solo when selecting one or more input solo controls, and
when the input solo is released, the output solo is re-established. A
master solo level trim control is located on the master module for
level matching, and the level of the solo signal is displayed on the
left mix bargraph.

An additional solo feature provided is Solo In Place. In this mode,
soloing any input channel will cause all other input channels to be
cut, thereby allowing only itself to be heard in the mix, correctly
panned and at the right level, along with any stereo effect return
channels. This is of great benefit during set-up and rehearsal and is
much more useful than the standard PFL. A switch on the master
module selects Solo In Place mode.

SIGNAL LED’s
The value of effective metering of signal levels throughout the
signal path cannot be overestimated. Signal present and 0dB LED’s
on all input channels give confidence to the operator while peak
overload LED’s indicate when the channel is being driven close to
clipping. However, it is unusual to find a peak overload LED at the
very place where it is most needed, at the summing bus mix
amplifiers, operating independently of the output meters. If the
mix amplifier is overloaded and starts to clip, the only thing that
can be done to rectify the situation is to pull down all input faders.
On the CS8, there are overload warning LED’s on each of the sub
group mix amplifiers as well as on the left, centre and right mix
amplifiers. When the output meters are switched to observe the
matrix outputs the bus peak leds also monitor the matrix bus.

INSERTS
Inserts are used to patch in external pieces of equipment such as
equalisers, limiters etc. and are provided on all channels, group
outputs, mix outputs and auxiliary outputs. To be useful and
useable, the inserts should be at a level which is compatible with
this external equipment. Sadly, this is often not the case. Some
mixers have inserts at odd levels which will preclude their efficient
use because of the noise penalty. All inserts on the CS8 are at a
consistent level which is at the internal operating level of 0dBu.

AUXILIARY INSER TS
In most installations, it is quite normal to place an equaliser in the
stage monitor sends, but this is normally external to the mixer. This
of course means that the only way of listening to the monitor sends
(internal to the mixer) is via the solo system.

6

Herein lies a problem. The operator does not hear the effect of the
external equalisation. Also, any noise introduced by the external
device is constant and not proportional to the setting of the send
control. The ideal place to insert an external device is pre the send
master control and this is the case in the CS8.

EQUALISER CUR VES
The following graphs illustrate the equalisation and filtering
responses of the CS8 console.

CS8HFLF HF/LF EQUALISER RESPONSE
CS8MID MID FREQUENCY EQUALISER BANDWIDTH

ADJUSTMENT

CS8MID1 MID FREQUENCY EQUALISER AMPLITUDE

ADJUSTMENT

CS8MID2 MID FREQUENCY EQUALISER FREQUENCY

ADJUSTMENT

CS8HP HIGH P ASS FIL TER RESPONSE

7

AUDIO PRECISION CS8HFLF vs 11 APR 97 11:31:21

20 100 1k 10k 20k

FREQ(Hz)

-20.00

-15.00

-10.00

-5.000

0.0

5.0000

10.000

15.000

20.000

AMPL(dBr)

AUDIO PRECISION CS8HPF vs 11 APR 97 11:43:15

20.000

15.000

10.000

5.0000

0.0

-5.000

-10.00

-15.00

-20.00
20 100 1k 10k 20k

AMPL(dBr)

FREQ(Hz)

THE HIGH AND LOW
FREQUENCY EQUALISER
RESPONSE

AUDIO PRECISION CS8HIMID vs 11 APR 97 11:37:11

20.000

15.000

10.000

5.0000

0.0

-5.000

-10.00

-15.00

-20.00
20 100 1k 10k 20k

AUDIO PRECISION CS8LOMID vs 11 APR 97 11:41:51

20.000

15.000

10.000

5.0000

0.0

-5.000

-10.00

-15.00

-20.00
20 100 1k 10k 20k

AMPL(dBr)

AMPL(dBr)

FREQ(Hz)

FREQ(Hz)

THE HI-MID FREQUENCY
EQUALISER RESPONSE
SHOWING FREQUENCY
RANGE

THE LO-MID FREQUENCY
EQUALISER RESPONSE
SHOWING FREQUENCY
RANGE

THE HIGH PASS FILTER
RESPONSE.

8

CS8 SPECIFICA TIONS

Nominal Operating Level +4dBu with a unity gain structure.

Frequency Response 20Hz - 20kHz +/-0.5dB any input to any output
at a gain < 50dB.

EQ range
HF +/-15dB @ 10kHz shelving
LF +/-15dB @ 100Hz shelving
Hi Mid +/-15dB 470Hz - 15kHz, Q = 1.4
Lo Mid +/-15dB 70Hz - 2.2kHz, Q = 1.4

Channel Routing Attenuation > 90dB @ 1kHz
Channel Mute Attenuation > 95dB @ 1kHz
Channel Fader Attenuation > 85dB @ 1kHz

Distortion

0.005% @1kHz any input to any output at a gain < 50dB.

Noise: -82dBu (24 channels routed and cut)
EIN: -127.5dBu ref 200 ohms
EIN: -128.7dBu ref 150 ohms

Maximum output level: +20dBu into a bridging load
Output impedance: <75R
Maximum input level: +30dBu
Phono connector levels: Nominal -10dBV

Signal present threshold: -21dBu
Peak led threshold: 3dB below clipping

Power consumption: < 600 Watts

OPTIONS

Input transformers Multipole connectors
Output transformers Bus linking cable
LED Meterbridge Flight case
VU Meterbridge Spare power supply with auto
Flight Case switchover

9

CS8 DIMENSIONS AND WEIGHTS

48 CHANNEL 1930.50mm(76.00")

40 CHANNEL 1681.50mm(66.20")

32 CHANNEL 1432.50mm(56.40")

MASTER AND

OUTPUT SECTION

4

STEREO

MODULES

16 CHANNEL 934.50mm(36.70")
24 CHANNEL 1183.50mm(46.60")

Meterbridge Widths:
VU 46.6 inches/1183.5mm (This cannot be fitted to a 16 input console)
LED As per corresponding console width.

Console weights (packed):

16 26.4kg/58lbs LED m/b 4.7kg/10.4lbs Combined 31.1kg/68.4lbs
24 36kg/80lbs LED m/b 6.0kg/13.3lbs Combined 42.0kg/93.3lbs
32 45.6kg/100lbs LED m/b 7.4kg/16.3lbs Combined 53.0kg/116.3lbs
40 55.2kg/122lbs LED m/b 8.6kg/19.0lbs Combined 63.8kg/141lbs
48 64.8kg/143lbs LED m/b 10.0kg/22.0lbs Combined 74.8kg/165lbs

VU Meterbridge 6.5kg/14.5lbs (Add to weight without LED meterbridge)

These weights assume a fully fitted console. Meterbridges are shipped in with
the console but not mounted on the console.

Power Supply Weight (packed): 7.8kg(17.2lbs)
Dimensions: 2U Rack Mounting with a depth of 265mm(10.43")

DIMENSIONS AND WEIGHTS

10

Declaration of Conformity

The Manufacturer of the Products covered by this Declaration is

Klark Teknik Building, Walter Nash Road, Kidderminster,

Worcestershire, DY11 7HJ.

The Directives Covered by this Declaration.

89/336/EEC Electromagnetic Compatibility Directive, amended by 92/31/EEC & 93/68/EEC
73/23/EEC Low Voltage Equipment Directive, amended by 93/68/EEC.

The Products Covered by this Declaration.

Model CS3 Mixing Console.
Model CS8 Mixing Console.
Model CS12M Mixing Console.

The Basis on which Conformity is being Declared

The products identified above comply with the protection requirements of the EMC Di­rective and with the principal elements of the safety objectives of the Low Voltage Direc­tive, and the manufacturer has applied the following standards:

EN 55013 : 1990
Limits and methods of measurement of radio disturbance characteristics of Broadcast

Receivers and Associated Equipment.
EN55020 : 1988
Sound and Television Broadcast Receivers and Associated Equipment, Electromagnetic

Compatibility.
EN 60065 : 1994
Safety requirements for mains operated electronic related apparatus for household

and similar general use.

The technical documentation required to demonstrate that the products meet
the requirements of the Low Voltage Directive has been compiled by the
signatory below and is available for inspection by the relevant enforcement
authorities. The CE mark was first applied in 1996

Signed: ................................ G.M.Squires

Authority: Product Support Manager.
Date: 1st, January 1997.

Attention

The attention of the specifier, purchaser, installer, or user is drawn to special
measures and limitations to use which must be observed when these products
are taken into service to maintain compliance with the above directives.
Details of these special measures and limitations to use are available on
request, and are also contained in product manuals.

11

INST ALLA TION GUIDE

There are a number of points to consider when installing a mixing
console. Many of these points will have been addressed before the
console is even unpacked but it is worth repeating them again.

POSITION
The console should be located in a convenient space commensurate
with the use to which the console is being put. Ideally a cool area is
preferred not in close proximity to power distribution equipment
or other potential sources of interference. Provision should be made
for some flat surface surrounding the console to prevent people
using it as a table top. One of the worst fates that can befall a
console is for a cup of coffee to be tipped into it by someone resting
it on the control surface!

POWER
The power supply should be located as far from the console as the
connecting cable will allow, a 5 metre power cable is supplied with
the console. It should be set for the appropriate line voltage and
plugged into the mains outlet using the supplied cable. If the power
supply is rack mounted then be sure to leave space above for
ventilation - 2U is suggested.

SLEEVE TIPRING

TIP CO NN EC TI ON

RING CON N ECTION

SLEEV E CONNECTION AND CABLE CLAM P

1/4 INCH TRS 'A' GAUGE JA C K PLUG

FEM A LE XLR-3MALE XLR-3

12

3

12

3

PHONO SO CK ETS

PHONO PLU G

12

WIRING
The console uses four different connector styles:­TRS jack sockets, XLR male connectors, XLR female connectors and
phono connectors.

The cables used should be of as high a quality as possible. Many
installation problems can be traced back to poor or faulty cables
and connectors.

There are two different conventions for the wiring of XLR
connectors. The international convention uses pin 2 as the hot pin
while the older American convention uses pin 3 as the hot pin.
When going from balanced input to balanced output this is of little
consequence but when unbalanced signals such as those found on
the insert points are used then phase reversal can result. The CS8
and all DDA products are wired PIN 2 HOT.

ATTENTION

CABLES
This product should only be used with high quality, screened twisted
pair audio cables, terminated with metal bodied 3-pin XLR
connectors. The cable shield should be connected to Pin 1. Any
other cable type or configuration for the audio signals may result
in degraded performance due to electromagnetic interference.

ELECTRIC FIELDS
Should this product be used in an electromagnetic field that is
amplitude modulated by an audio frequency signal (20Hz - 20kHz),
the signal to noise ratio may be degraded. Degradation of up to
60dB at a frequency corresponding to the modulation signal may
be experienced under extreme conditions (3V/m, 90% modulation).

No permanent damage or degradation of performance will be
caused by these conditions.

13

CIRCUIT DESCRIPTIONS

The following gives a brief description of each module as an aide
to understanding the signal flow within the console. Many
references are made to the circuit diagrams with the reference
number for the appropriate diagram being given at the beginning
of each module. The master module uses two circuit boards
requiring four circuit diagrams.

INPUT MODULE (CD1279)

The input module contains eight input channels mounted on a
common set of metalwork. The channels are identical and a console
is constructed by using 2 or more input modules together with an
output module and a master module within a frame.

THE INPUT ST AGE (CD1279)
The same input stage is used for both the microphone and the line
input. CON2, an XLR style connector, is used for the microphone
input which is wired to the inner contacts of CON3, the line input
TRS jack. With nothing inserted into the jack socket the signal
connects to the normal contacts and is then fed to an attenuator
which is activated by selection of the line input. Resistors R2 and
R3 feed phantom power to the microphone input and this is DC
blocked from the line input amplifier by C2 and C3. SP1, SP2 and
SP6 are filters providing protection from high frequency signals
entering the inputs. Additional filtering is carried out by capacitors
C37, C38, C39 and C40. CON9 (optional) is wired in parallel with
the XLR which allows for wiring the input to a multipole connector
mounted on the console frame.

Resistors R7, R8 and R9 form an attenuator when the line input is
selected, reducing the input signal by 30dB. C45 and C46 again
provide DC isolation and there is provision at this point for the
insertion of an input balancing transformer. Note that if a
transformer is fitted R14 should be changed to 1k. Where a
transformer is not fitted two 10R resistors (R10, R11) carry the signal
through to the input amplifier. D1, D2, D3 and D4 provide clamping
for excessive input voltages and the signal is applied to the bases
of transistors Tr5 and Tr7. VR1 is the front panel gain control and
this is connected through the MIC/LINE switch such that in the MIC
position the gain range is 20 to 70dB while in the LINE position it is

-10 to 20dB.

Signal is taken from the collectors of Trs 5 and 7 and applied
differentially to the input of IC1A. The output from here is fed
back to the emitters of the input transistors through 56k resistors
with one side being phase inverted by IC1B. The phase reverse

14

switch, SW3, selects either the normal or the phase inverted signal
and feeds it to the high pass filter stage. This is a three pole high
pass filter operating at 80Hz giving a roll off of 18dB per octave.
When not required this can be completely bypassed by SW4. The
output of SW4 after buffering by IC8B is known as PRE1 and is the
pre equaliser signal. PRE1 is a source for the auxiliary sends which
will be referred to later.

THE EQUALISER
The signal is presented to the equaliser which is a four band design.
The high and low frequency sections are built around IC2B with
VR7 providing low frequency boost and cut while VR2 provides
high frequency boost and cut. The middle frequency sections are
built around IC3 and use a Wein bridge as the frequency
determining network. VR3 selects the frequency of operation and
VR4 determines the amount of boost or cut given to the hi mid
signals while VR5 alters the frequency and VR6 the boost or cut for
the lo mid signals. The output from the equaliser connects to SW5
the EQ IN/OUT switch where either the pre equaliser sinal or the
equalised signal can be selected to be passed to the insert send.

CON5, a Tip, Ring and Sleeve jack, is used for the insert point with
the Tip being used as the send. SP3 and SP4 are filters preventing
noise from entering the console. The insert return signal is buffered
by IC7A and is then presented to the channel fader. The output
from the fader feeds the channel cut circuit.

The pre fader signal feeds the auxiliary cut circuit, the solo bus
when a solo is requested and finally the 3 led signal meter which is
driven from IC6, a quad comparator. There are SIGNAL PRESENT,
0dB and PEAK indicators which are powered from a current source
built around Tr8. The auxiliary cut allows the creation of a PRE
FADE POST MUTE signal, which can be defeated if required, in
addition to the POST FADE POST MUTE signal.

THE MUTE CIRCUIT
Tr1 is the CHANNEL MUTE fet which is buffered by IC4A and
following this the signal is known as POST. This signal routes to the
groups when panning is not used and also feeds the auxiliary sends
when selected as POST. The pre fade signal goes through a second
AUXILIARY MUTE circuit built around Tr2 to give a PRE FADE POST
MUTE signal called PRE2. LK1 is normally installed allowing the
PRE FADE signal to be muted when the channel mute is operated.
By removing LK1 and installing LK2 the PRE FADE signal will not
mute with operation of the channel mute switch.

15

In order to improve the attenuation of the mute circuits a small
amount of signal is fed forward to cancel with any residual from
the output of the fets. Resistors R140, R141 and R142 perform the
feed forward for the channel signal while R99, R100 and R101 are
used for the auxiliary cut circuit.

The mute circuit can be remotely controlled either through the
external remote connector or from the four mute groups provided.
A SAFE button allows the mute groups to be disabled on the
module. When the local mute button is pressed a ground is placed
onto the remote control connector. This can be used to operate
external equipment such as a midi sequencer or it could be
connected to other channels so that when one channel is muted
others will also mute. Led 1 indicates a MUTE whether it is local or
remote. In every case a MUTE request grounds the base of Tr6
causing it to switch off and hence its collector to go high. This is
applied to the gates of Tr1 and Tr2 causing them to switch off since
they are P channel fets. Tr4 will also turn off causing Tr3 to turn off
allowing led 1 to indicate the mute condition.

THE P AN CIRCUIT
The POST signal next goes to the pan circuit. This circuit can be
switched between stereo (L/R) and left/centre/right (LCR) modes
using SW15. The output of the pan pot can be routed to the mix or
the groups. If panning to groups is not selected then the groups
receive the POST signal while, with panning selected, they receive
the output of the pan pot (PANL and PANR). If LCR panning is
selected then assigning to mix (SW13) will send signal to the left
centre and right buses.

If L/R mode is selected no signal will appear on the centre output
except by pressing the MONO button (SW27) when the POST signal
will be routed to the centre bus. The groups can only use the left
and right pan pot outputs and therefore if LCR panning is selected,
panning to groups will not function in the expected manner.

The pan pot is built around VR16, a dual pot, and IC5. When in L/R
mode only one section of the pot (VR16A) is used and it simply
reduces the resistance to ground of the left or right signal
depending upon the direction of rotation. This reduces the
amplitude of the signal on one side while increasing it on the other
to create the panning effect.

When LCR mode is selected the input signal is fed to a centre tap
on VR16A. Signal can thus only appear on the left or right output
of this section of the pan circuit (but not both together) with the
amplitude depending again on the rotation of the pan pot.

16

The centre output is derived from the same input signal and VR16B
is used to control its amplitude by decreasing the resistance to
ground when the pot is rotated away from its central position.
IC5B buffers the centre signal.

THE AUXILIARY SENDS
The auxiliary sends can use the following three signals :­PRE1, PRE2 and POST.

PRE1 is the pre equaliser signal, PRE2 is the pre fader post mute
signal and POST is the post fader post mute signal.

All auxiliaries will normally receive the POST signal, however, there
are PRE switches associated with the auxiliaries allowing the pre
fader signal to be selected. The default condition is that PR2 shall
be the pre signal although links allow this to be changed to the
PRE1 signal. Only one link of a pair should ever be inserted.

Auxiliaries 1, 2, 3
Link 4 PRE1
Link 3 PRE2

Auxiliaries 4, 5, 6
Link 5 PRE1
Link 6 PRE2

Auxiliaries 7, 8
Link 7 PRE1
Link 8 PRE 2

THE SOLO FUNCTION
SW22 is the solo or PFL switch. When operated it places DC onto
the IPCUEDC bus which is detected by the master module. The audio
signal INS_RET is fed onto the IPCUE bus and fed to the monitoring
system on the master module. If Solo In Place mode is selected
then the module initiating the solo will have its solo switch
depressed and the incoming SIP signal will have no effect. If the
module did not originate the solo in place the solo switch will not
be depressed and the SIP signal will cause the channel to mute.

THE DIRECT OUTPUT
The direct output is available at CON5, a jack connector. The signal
is unbalanced, at a nominal level of 0dBu and by default is the
POST signal. SW28 allows the PRE1 signal to be used.

17

Switches 9, 10, 11, 12, 23, 24, 25 and 26 route the signal to the
groups. Switch 27 routes signal to the MONO (CENTRE) bus and
SW13 routes to the stereo MIX bus.

ROUTING AND MUTE GROUPS
Switches 18, 19, 20 and 21 select the mute group buses. They are
combined through diodes D11 through D14 and then go to the
SAFE switch SW17 before combining with the local and remote
MUTE signals.

GROUNDING
All routing to buses is through 10k resistors. All connectors are
grounded to the metalwork (chassis) ground. This is connected to
0V by a 100R resistor in parallel with a 10n capacitor. BUSREF is
taken from 0V through a 10k resistor.

There is provision for an external meter output on CON8 (option).

18

INPUT MODULE LINKS

INPUT MODULE PC1394

LIN K FU N CTION

1AUXILIARY CUT ENA BL E YES

2AUXILIARY CUT DISA BLE

3PRE FA D ER TO AUX 1-3YES

4PRE EQ TO AUX 1-3

5PRE EQ TO AUX 4-6

6PRE FA D ER TO AUX 4-6YES

7PRE EQ TO AUX 7-8

8PRE FA D ER TO AUX 7-8YES
9N/A

10 N /A

11 PRE EQ TO DIR OUT YES

12 PO ST EQ TO DIR OUT

FI TTED AS

SU PPLI ED

NOTES

INSTALL

ONLY ONE

LINK

INSTALL

ONLY ONE

LINK

INSTALL

ONLY ONE

LINK

INSTALL

ONLY ONE

LINK

INSTALL

ONLY ONE

LINK

19

MONO

MIX RIGHT

MIX LEFT

INPUT MODULE BLOCK DIAGRAM

MUTE GROUP 4

MUTE GROUP 3

MUTE GROUP 2

MUTE GROUP 1

PFL

AFL

AUXILIARY 8

AUXILIARY 7

AUXILIARY 6

AUXILIARY 5

AUXILIARY 4

AUXILIARY 3

AUXILIARY 2

AUXILIARY 1

GROUP 8

GROUP 7

GROUP 6

GROUP 5

GROUP 4

GROUP 3

GROUP 2

GROUP 1

56

12

34

ROUTING

78

TO GROUPS

PAN

+/-

15dB

freq.

4 BAND EQUALISER

HI

LO

GAIN

20 to 70dB

-10 to20dB

GAIN

OPTIONAL TX

INPUT

OPTION:

INPUT

MULTIPOLE CONNECTOR

MONO

EQ

HFLF

HI

MID

LO

MID

HPF

PHASE

LK11

LK12

48V

MIX

SIS

PAN

FADER

OUTPUT

EXTERNAL METER

PRE

DIR

SIS

+10dB

PEAK

0dB

DIRECT OUTPUT

LK1,2

SIGNAL PRESENT

1

PRE

LK3

PFL

EXTERNAL MUTE IN/OUT

CHANNEL

1

INSERT POINT

2

LK4

MUTE

3

SAFE

3

PRE

6

4

7

5

8

PRE

LK6

LK5

LK8

LK7

123

4

MUTE GROUP 1

MUTE GROUP 3

MUTE GROUP 2

MUTE GROUP 4

20

THE STEREO INPUT MODULE (CD1302/3)

THE INPUT ST AGE
The same input stage is used for both microphone and line inputs.
Looking at the left signal path, CON2, an XLR style connector, is
used for the microphone input which is wired to the inner contacts
of CON3, the line input TRS jack. With nothing inserted into the
jack socket the signal connects to the normal contacts and is then
fed to an attenuator which is activated by selection of the line
input. Resistors R2 and R3 feed phantom power to the microphone
input and this is DC blocked from the line input amplifier by C2
and C3. SP1, SP2 and SP3 are filters providing protection from high
frequency signals entering the inputs. Additional filtering is carried
out by capacitors C37, C38, C39 and C40.

Resistors R7, R8 and R9 form an attenuator when the line input is
selected, reducing the input signal by 30dB. C45 and C46 again
provide DC isolation and there is provision at this point for the
insertion of an input balancing transformer. Note that if a
transformer is fitted R14 (R214) should be changed to 1k. Where a
transformer is not fitted two 10R resistors (R10, R11) carry the signal
through to the input amplifier. D1, D2, D3 and D4 provide clamping
for excessive input voltages and the signal is applied to the bases
of transistors Tr4 and Tr5. VR1A is the front panel gain control and
this is connected through the MIC/LINE switch such that in the MIC
position the gain range is 20 to 70dB while in the LINE position it is

-10 to 20dB.

Signal is taken from the collectors of Trs 4 and 5 and applied
differentially to the input of IC1A. The output of IC1A is fed back
to the emitters of the input transistors through 27k resistors with
one side being phase inverted by IC1B. The phase reverse switch
SW28 (located in the left signal path only) selects the normal or
phase inverted signal and passes it to the high pass filter formed
around IC2A. This is a three pole high pass filter operating at 80Hz
giving a roll off of 18dB per octave. When not required this can be
completely by-passed by SW3. The output of SW3 passes through
SW19, the MONO R switch to become PRE-L1 which is the pre
equaliser signal (left). It is a source for the auxiliary sends which
will be referred to later.

SUMMING AMPLIFIER
IC11A sums the left and right signals together to create a mono
signal which has its polarity restored by IC11B before being
presented to switches SW19 and SW20 (the left and right signal
cut switches). When Mono R (switch 19) is pressed the left signal is
cut and replace by the right signal. Similarly when Mono L (switch

20) is pressed the right signal is cut and replaced by the left signal.
If both switches are pressed the output of IC11B (a mono signal) is
fed to both left and right signal paths.

21

THE EQUALISER
PRE1 L1 is presented to the equaliser which is a four band design.
The high and low frequency sections are built around IC9A with
VR6 providing low frequency boost and cut while VR2 provides
high frequency boost and cut. The lo middle frequency section is
built around IC8/IC202A. VR15 selects the frequency of operation
and VR14 determines the amount of boost or cut given to a signal.
The hi middle frequncy section is built around IC15B and IC16A.
VR17 determines the frequency of operation while VR18 determines
the amount of boost or cut. The equaliser output feeds the EQ IN/
OUT switch, SW29 allowing the pre or post equaliser signal to be
selected.

IC7A buffers the equaliser output and feeds it to the fader. The
equaliser output is also used to derive the PFL signal and to drive
the SIGNAL PRESENT, 0dB and PEAK indicators.

THE CUT CIRCUIT
The signal path splits at this point to go through two cut circuits.
This allows the creation of a PRE FADE POST MUTE signal (which
can be defeated if required) in addition to the POST FADE POST
MUTE signal. Tr1 is the CHANNEL MUTE fet and the post cut signal
is buffered by IC4A. The signal leaving IC4A is the POST FADE signal
which is then fed through a pan pot that can be routed to the
groups or the L/R mix. The pre fade signal goes through an
AUXILIARY MUTE circuit built around Tr2 to give a PRE FADE POST
MUTE signal called PRE2. LK1 is normally installed allowing the
PRE FADE signal to be muted when the channel mute is operated.
By removing LK1 and installing LK2 the PRE FADE signal will be
unaffected by operation of the channel mute switch. IC12A is used
to combine the left and right post fade signals for sending to the
auxiliaries. IC12B is used to combine the left and right pre fade
signals for sending to the auxiliaries.

As with the input module a small amount of signal is fed forward
to cancel any residual from the fets to improve the mute
attenuation.

THE BALANCE CIRCUIT
The post fade signal next goes to the balance circuit. The output of
the balance pot can be routed to the mix or the groups. The groups
normally receive the mono post fade signal but with the PAN switch
depressed they will receive the outputs of the balance pot built
around VR16. By default the balance control works as a pan pot
with full attenuation of the unwanted side. A more limited range
of adjustment can be obtained by changing the circuit as follows :-

22

Move R140 to R141 and R341 to R340 leaving the positions for
R140 and R341 blank.

Make R142 and R342 both 10k (they are 0R links).

This will then give a balance range of +3/-6dB.

PEAK AND SIGNAL PRESENT LEDS
A PEAK indicator and a SIGNAL PRESENT indicator are driven from
the post equaliser signal. IC14 is used as a voltage comparator and
directly drives leds 5 and 6. A reference voltage is applied to pins 5
and 7 while audio is applied to pins 3 and 5. The PEAK led comes
on 3dB before clipping while the SIGNAL PRESENT led comes on
with a signal level higher than -18dBu.

THE AUXILIARIES
With the exception of auxiliaries 7 and 8 the auxiliaries work in
mono using mixed left and right signals which are derived either
pre or post fade. The following three signals are available :­PRE1, PRE2 and POST.

PRE1 is the pre equaliser signal, PRE2 is the pre fader post cut signal
and POST is the post fader post cut signal.

When PRE is selected the PRE2 signal is the factory default setting.
Links enable the default settings to be changed.

AUX 1-3
Remove link 3 and install link 4 for PRE1.

AUX 4-6
Remove link 6 and install link 7 for PRE1.

AUX 7-8
Remove link 11 and install link 12 for PRE1.
Auxiliaries 7 and 8 may be used as a stereo pair by depressing SW22,
the STEREO switch.

23

THE CUT CIRCUIT LOGIC
SW6 is the mechanically latching CUT switch which when operated
places a ground on the cathode of D15 causing the base of Tr3 to
go low and therefore the collector to go high. D9 will now stop
conducting enabling LED1 to illuminate indicating a cut. The
collector of Tr3 is applied via R118 and R98 to the gate of Tr1, an P
channel FET, causing it to stop conducting hence muting the signal.
D10 is used to create different on and off switching times for the
FET.

As the attenuation of the FET is not perfect a feedforward technique
is used to cancel any residual signal. A small fraction of the channel
signal is fed to the non inverting input of IC4A where it will sum
with the residual but in anti-phase to it thus cancelling it completely.
The operation of the AUXILIARY CUT is similar to that of the
CHANNEL CUT. Links 1 and 2 exist to disable the auxiliary cut if
required. In this case Link 1 should be removed and Link 2 installed.

An external input and output are available for the CUT function.
The external cut output simply extends a ground onto the connector
when the cut switch is depressed. The external cut input requires
to ground the cathode of D7 which then has the same effect as the
cut switch grounding D6. A simple latching switch contact is
sufficient.

THE SOLO FUNCTION
SW18 is the solo or PFL switch. When operated it places DC onto
the IPCUEDC bus which is detected by the master module enabling
it to replace the selected monitor signal with signal from the solo
bus (IPCUE). The equaliser outputs are mixed to mono for use as
the solo signal. If Solo In Place mode is selected then the module
initiating the solo will have its solo switch depressed and the
returned SIP signal from the master module will have no effect. If
the module did not originate the solo in place the solo switch will
not be depressed and the SIP signal will cause the channel to mute.
Thus only the module initiating the solo will be left uncut. In this
mode no change takes place on the master module and only the
module initiating the solo in place will be heard through the
monitoring system.

There is provision for an external meter on connector CON4 (option).

ROUTING AND GROUNDING
All routing to buses is through 10k resistors. All connectors are
grounded to the metalwork (chassis) ground. This is connected to
0V by a 100R resistor in parallel with a 10n capacitor. BUSREF is
taken from 0V through a 10k resistor.

24

STEREO INPUT LINKS

STEREO INPUT MODULE PC1418

LINK FU NCTION

1

2

3

4

6

7

11

12

AUXILI ARY CUT

ENA BLE (LEFT)

AUXILI ARY CUT

DISA BLE (LE F T )
PRE FA D ER MONO

TO AUX 1-3

PRE EQ MONO TO

AUX 1-3

PRE FA D ER MONO

TO AUX 4-6

PRE EQ MONO TO

AUX 4-6

PRE FA D ER MONO

TO AUX 7-8

PRE EQ MONO TO

AUX 7-8

FI TTED AS

SU PPLI ED

YES

YES

YES

YES

NOTES

INSTA LL ONLY

ONE LINK

INSTA LL ONLY

ONE LINK

INSTA LL ONLY

ONE LINK

INSTA LL ONLY

ONE LINK

17

18

21

22

201

202

PRE EQ LEFT TO

AUX 7-8

PRE EQ RIGHT TO

AUX 7-8

PRE FA D ER LEFT

TO AUX 7-8

PRE FA D ER RIGHT

TO AUX 7-8
AUXILI ARY CUT

ENA BL E (RIGHT)

AUXILI ARY CUT

DISA BLE (RIGHT)

25

FI T AS A PA IR

YES

FI T AS A PA IR

YES

YES

INSTA LL ONLY

ONE LINK

STEREO INPUT MODULE BLOCK DIAGRAM

MUTE GROUP 4

MUTE GROUP 3

MUTE GROUP 2

MUTE GROUP 1

PFL

AFL

AUXILIARY 8

AUXILIARY 7

AUXILIARY 6

AUXILIARY 5

AUXILIARY 4

AUXILIARY 3

AUXILIARY 2

AUXILIARY 1

GROUP 8

GROUP 7

GROUP 6

GROUP 5

GROUP 4

GROUP 3

GROUP 2

GROUP 1

MONO

MIX RIGHT

MIX LEFT

8

1234567

FADER

ROUTING

+/-

15dB

freq

4 BAND EQUALISER

R BOTH

HI

LO

GAIN

20 to 70dB

-10 to20dB

GAIN

INPUT

OPTION:

MULTIPOLE CONNECTOR

HI

LO

HPF

MID

MID

LF HF

PHASE

EQ

STER

MIX

MONO

7

3

1

2

6

4

5

8

HI

LO

MID

MID

LF HF

L BOTH

PRE

HPF

PRE M1

BALANCE

PRE

POST M

PRE M2

PRE

STEREO

GAIN

PEAK

123

PRE L1

PRE R1

PRE L2

PRE R2

SIGNAL

OdB

MUTE

SAFE

4

PFL

LEFT INPUT

48V

RIGHT INPUT

INPUT

OPTION:

MULTIPOLE CONNECTOR

26

OUTPUT

OPTION:

EXTERNAL METER

EXTERNAL MUTE IN/OUT

1

3