ALLEN & HEATH SCEPTER User manual

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SCEPTER
12 channel
Rack Mount Mixer
OWNER MANUAL
Allen & Heath Publication:
APO093 Issue 3
October 92
OWNER MANUAL

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ALLEN & HEATH
This product continues ALLEN & HEATH’s commitment to provide
high quality tools engineered to meet the exacting requirements of
today’s audio business. It brings you the latest in high
performance technology and offers the reassurance of over two
decades of audio console manufacture and customer support.
Whilst we believe the information in this manual to be correct and
reliable we do not assume responsibility for any errors or
omissions. We also reserve the right to make changes in the
interest of further product development.
We are able to offer you further product support through our
network of approved dealers and service agents. To help us
provide the most efficient service please would you return your
completed WARRANTY REGISTRATION card, and enter the
following details below to be quoted in any communication
CONSOLE model:
I1 serial number: I1
POWER UNIT model:
serial number:

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ALLEN & HEATH BRENELL LTD.
LIMITED ONE YEAR WARRANTY
This product has been manufactured in the UK by ALLEN & HEATH
BRENELL LTD and is warranted to be free from defects in materials or
workmanship for a period of one year from the date of purchase by the
original owner.
To ensure proper validation and handling of warranty services please
return the WARRANTY REGISTRATION CARD,.
To ensure the high level of performance and reliability for which
this equipment has been designed and manufactured, please read
the Owner Manual before use.
In the event of a failure notify and return the defective unit to ALLEN &
HEATH or its authorised agent as soon as possible for repair under
warranty subject to the following conditions:
CONDITIONS OF WARRANTY:
1. The equipment has been installed and operated in accordance with the
instructions in the Owner Manual,
2. The equipment has not been subject to misuse either intended or accidental,
neglect, or alteration other than as described in the Owner/Service Manual,
or approved by ALLEN & HEATH.
3. Any necessary adjustment, alteration, or repair has been made by ALLEN
8z HEATH or its authorised agent,
4. The defective unit is to be returned carriage prepaid to ALLEN & HEATH
or its authorised agent and proof of purchase made available on request,
5. Units to be returned should be packed to avoid transit damage and be
accompanied by the Power Supply Unit.
These terms of warranty apply to UK sales. In other territories the terms
may vary according to legal requirements.
ALLEN & HEATH AGENT:
FACTORY:
ALLEN & HEATH BRENELL LTD
Kernick Industrial Estate
Penryn
Cornwall TRlO 9LU
A Harman international Company

Allen & Heath
CONTENTS PAGE
1
...... INTRODUCTION
GeneralInformation
. .........................
................
1
Safety & Precaution
..........................................
2
installation
........................................................ 3-4
User Service Information...................................
5
ElectronicPerformance ..................................... 6-7
2 ...... PANEL CONTROL DIAGRAMS
InputChannels
................................................. 8-9
L/R Section
.............. ......................................... 10-11
MasterSection
........ .........................
................ 12-13
Rear Panel .............. .........................
................14-16
3 ...... USE
OF FACILITIES
FRONT PANEL CONTROLS
Input Channel Section
.......................
................17-20
Left/Right Section
.............................................
21
MasterSection
........ .........................
................22-23
4 . . . . . . REAR
PANEL CONNECTORS
Input Channel Section
.......................
................24
L/R Section..............
........................................ ,25-26
MasterSection
.................................................
27-28
D.C. Power connector
.......................
................ 29
5 ...... USER
CONFIGURED OPTIONS
Access to Mixer Circuits
....................
................ 30-31
Options Descriptions
.........................
................32
DirectOutputs
.................................................. 32
Chan Aux Sends
.*.a* ......................................... 33-34
Stereo Rtn Aux Sends
.......................
................34
Mono & Stereo Output ...................................... 35
User Options Table .........................................
.36
Chassis Ground Isolation ..................
................37
.........................................................
................ continued

Allen & Heath
CONTENTS continued
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6
. . . . . . SERVICE
INFORMATION
DIAGRAMS
Main IDC Ribbon Connector
. . . . . . . . . ...* ..*...,.........
DimensionsDiagram . . . . . . . . . ..*......*......
..*.....*.*..*..
System Block Diagram
.,..*.*..*.....*..,...
. . . . . . . ...*.....
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7......
SCHEMATIC DIAGRAMS
Input Components and Option Placement..
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Input Circuit Diagram ........................
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Left / Right Components and Option Placement
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Left / Right Circuit Diagram
............... ................
Master Components and Option Placement..
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Master Circuit Diagram ......................
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EBOS Components
& Circuit Diagram...............
Power Supply Components & Circuit Diagram . .
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Audio Owner Manual Section 1
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INTRODUCTION
The Allen & Heath SCEPTER RACK MOUNT MIXER is a versatile,
economical and easy-to-use general purpose rack mount mixer intended for stereo
and mono PA applications as well as stereo recording. The quality of design,
construction and components employed will ensure high performance in these
applications when correctly used. Operators and installers are encouraged to study
the contents of this handbook.
Construction:
1.
Aluminum front panel, stove enamel, enamel silk-screened legend.
2.
Steel Rear Panel and Chassis, grey stove enamel finish.
3.
Individual Channel assemblies secured to Front and Rear panels.
4.
Internal busbar circuits employ removable IDC harness.
5.
Glass-epoxy circuits cards for strength and reliablity
6.
All audio path ICs are socketed for ease of service.
7. IC op-amp and discrete component circuit design.
AC Power Requirements:
Allen & Heath power supplies MPS8-R (Supplied), MPS8-P, MPS9, and RPS-1
provide the necessary DC power for the mixer. These are the only power supplies
recommended for use with this product. Use of power supplies other than those
specified may void the mixer warranty. All Allen & Heath power supplies operate on
the following mains voltages/frequencies -
220-240V AC 50/60 Hz 50VA Europe
11 O-1 20V AC 50/60 Hz USA
100 Volt AC 50/60 Hz 50VA Japan
NOTE: The MPS-8R power supply is provided as standard with the Scepter.
providing +15 Volts and -15 Volts for mixer operation, and +48 Volts for Phantom
Power microphone operation. It is configured as a Rack Mount Power Supply for
standard 19” racks. If necessary the Front Panel may be removed to enable remote
mounting.
Further details on mains voltages are available within the SERVICE section of
this manual.
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Audio Owner Manual
Section 1
Mains electricity is dangerous and can kill. Mains voltage is present within the
power unit but not the Scepter unit. Check your mains wiring and earthing before
connecting up and switching on.
The purpose of the “earth” (ground) connection in a mains supply is for the
prevention of electric shock from the mains voltage present. It is usual for the
chassis of mains powered equipment to be connected to earth to prevent the metal
parts becoming “live” and causing electric shock. Some are “double insulated” and
do not require an earth connection.
The Scepter power supply (MPS-8R) must be connected to a suitable mains
earth through the designated earth wire in the mains cord.
The power supply mains earth is not connected to the Scepter earth. The unit
should be connected via a different path to mains earth. (see CHASSIS GROUND
LIFT section)
Equipment will continue to function if it is not connected to mains earth.
This does not mean that it is safe. GOVERNMENT AND INSURANCE
UNDERWRITERS ELECTRICAL CODES MUST BE OBSERVED. These codes
take precedence over any suggestions in this manual.
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Audio Owner Manual Section 1
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INSTALLATION
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Unpack the unit from the packing carton. Remove the power supply unit from
the packing. We recommend that you keep intact this purpose designed packing to
reuse should you need to ship the unit in the future. Please ensure that the Scepter
unit, power supply and other items are correctly repacked to avoid transit damage.
Please ensure that the fader knobs are in the up position.
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Check that the AC operating voltage marked on the power unit is the same as
the local supply.
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Connect the DC power cord from the power supply into the rear panel of the
Scepter unit. Ensure that it latches firmly.
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Earthing/Grounding in the audio system
There two important reasons why it is necessary to ensure that your audio
system is well earthed (grounded).
1)
Safety - prevention of electric shock (see previous section on SAFETY)
2)
Shielding - preventing external electrical interference from causing noise in the
audio signal path.
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In addition to solving noise and interference problems, earthing can also
cause them. If there are multiple earth paths in a system then an “earth loop” can
be formed. This usually results in an excess hum in the system, but can also cause
the breakthrough of RF and other noises.
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The preferred method to overcome earth loop problems is to earth all pieces
of equipment separately to a good “star point” mains earth and to break potential
earth loops by disconnecting the screens of the audio cables at one end, usually
the signal destination. If excessive RF interference is present this may be reduced
by connecting the screen to earth through a small value capacitor, typically 0.01
microfarad
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Alternatively; just one piece of equipment, usually the power amplifier, is
connected to mains earth and the other equipment earthed via the interconnecting
cable screens which must be connected at both ends. However, having only one
unit connected to mains earth means that all of the other pieces of equipment rely
on the audio cable screen for safety. It is important to remember this. Test
regularly, that all exposed metal equipment including microphones, guitar strings
and DI boxes have a low resistance to mains earth.
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Audio Owner Manual Section 1
The console is not connected to mains earth for the reasons mentioned above
and under normal operating conditions it contains no dangerous voltages. The
power supply chassis is connected to mains earth and must never be
disconnected. Likewise never disconnect the earth wire in the mains plug.
It is best to plan ahead and have your installation checked by a competent
engineer before you commence. Do not trust equipment and installations modified
by others.
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Audio Owner Manual Section
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USER SERVICE INFORMATION
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There are no adjustments or alignment procedures required to maintain the
performance standards of this Allen & Heath product.
To preserve the working life of the unit and its presentation, avoid the use of
chemicals, abrasives and solvents. The control panel is best cleaned with a soft
brush and a damp cloth. Switches and potentiometers are lubricated for life; the
application of electrical lubricants to these parts is not recommended.
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A number of user options are available. These are changes to the functions of
various controls and outputs which can be altered by the user repositioning internal
jumper links. The details of these options are covered under in USER
CONFIGURED OPTIONS section of this manual. Any modifications to the unit other
than those specifically listed will automatically void the warranty.
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Audio Owner Manual
Section 1
ELECTRONIC PERFORMANCE
OdBu - 0.776 Volts RMS 1 kHz
OVU = +4dBu = 1.23 Volts RMS
Unreferenced dB represents Voltage Gain
MAX VOLTAGE GAIN:
Figures include 10dB input and group fader boost
MIC IN to L/R Out
,.., ,,,.........I*.........*.
+80dB
LINE IN to L/R Out . . . . . . . . ..*..........*....* +62dB
L/R to Mono Out
..,.,. ... ..**......*.......s.*.
+1 OdB
FX RETURN to L/R Out . . . . . . . . . . . . . . . . . . . . +24dB
INPUTPAD ..a.....,.... ,,,...................... -16dB
INPUT GAIN CONTROL RANGE......52dB
.*.............**...*.....***... . . . ..*...*..............* 70dB with Pad
FREQUENCY RESPONSE:
Equalizer set to flat response or switched out
. . . . . . . . . . . . . . 20Hz to 20kHz+0/-l dB.
INTERNAL OPERATING LEVEL=
. . . ..*......**............* Channel= OdBu; L/R=-2dBu
ALL OUTPUTS AND INSERTS IN-PHASE REF TO XLR PIN 2 INPUT
AND l/4” TIP CONNECTOR.
OUTPUTS: LEFT
- RIGHT - MONO
Self Compensating Electronically Balanced
Capable of Balanced or Unbalanced operation
Max level +27dBu Bal, +2ldBu Unbal
Recommended load 600 ohms or greater
Connectors - 3 pin XLR Type
Pin 1 = Gnd (with lift switch)
Pin 2 = +
Pin 3 = -
When pin 2 or 3 grounded, Opposite output pin gain is increased by 6dB
ALL OTHER MONO OUTPUTS
Unbalanced; Max level +21 dBu
Recommended load 600 or more:
2k or more for Channel Insert & Direct Out
Connector - l/4” Phone Jack
Tip is +, Ring and Sleeve= ground
DISTORTION:
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Audio Owner Manual
Section 1
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ELECTRONIC PERFORMANCE continued
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THD typically better than 0.04%
20Hz-20kHz at ‘normal levels and gain settings
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NOISE PERFORMANCE: RMS noise 20kHz bandwidth
L or R Output(all input faders closed)-83dBu
L or R Output(1 input @ unity gain)-83dBu
Aux Outputs(Unity gain)-90dBu
Microphone Input equivalent noise-l 27dBu (200 Source)
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Audio Owner Manual Section 2
LINE
L-J
PAD
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AUX SENDS
HF -0+
MID - ? +
E
III
EQ IN
FRONT PANEL CONTROLS.
INPUT CHANNEL
1.
2.
3.
4.
5.
6.
7.
6.
9.
10.
GAIN
Adjusts the gain of the input pre-amplifier to suit input levels.
Control range is +18 to +66dB (mic) and -4 to +43dB (line).
LINE
Selects between Microphone and Line input sources. With the
switch engaged, Line input is selected.
PAD
When selected, reduces the input signal level by approximately
16dB.
AUX SENDS A,B,C,D
Allows the operator to create up to four different mixes to be
used as foldback, effects or cue mixes as desired. The
SCEPTER mixer is delivered from the factory with AUX SENDS
A and B set for PRE-FADER operation. AUX SENDS C and D
are set for POST-FADER operation. Internal jumpers are
provided to allow custom configuration of all Aux buses.(SEE
USER OPTIONS)
HIGH FREQUENCY EQUALIZER
Boosts or cuts the High Frequencies by up to 16dB at the
corner frequency of 1OkHz with Shelving characteristics.
MID FREQUENCY SWEEP CONTROL
Selects the center frequency affected by the mid frequency gain
control. Continuously variable from 250Hz to 6 kHz.
MID FREQUENCY EQUALIZER
Boost or cuts the Mid Frequency by up to 12dB. Approximately
1 octave around the center frequency with Peak/Dip
characteristics
LOW FREQUENCY EQUALIZER
Boost or cuts the Low Frequencies by up to 16dB at the corner
frequency selected by the Low Frequency Select Switch.
LOW FREQUENCY SELECT SWITCH
Selects the corner frequency of the Low Frequency Equalizer
between 12OHz(Up) and GOHz(Down).
EQ IN
With this switch engaged, the EQ section is active in the
channel. With the switch released the EQ section is bypassed.
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Audio Owner Manual Section 2
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PFL
B PEAK
&IG 0 *
1
FRONT PANEL CONTROLS - INPUT CHANNEL (cant)
11.
HIGH PASS FILTER SWITCH
Causes a gradual roll off in level of all frequencies below 80Hz
at a rate of -12dB per octave. Useful in eliminating unwanted
low frequency sounds.
12.
PAN CONTROL
Positions input signal anywhere between the Left and Right
outputs of the stereo mix. Full counter-clockwise routes all of
the input signal to the left channel. Full clockwise routes all of
the input signal to the right channel. With this control centered,
an equal amount of signal is routed to the Left and Right
channels.
13.
MUTE SWITCH (with LED Indicator)
Cancels or mutes the channel and all of its auxiliary sends
(SEE USER OPTIONS), but does not affect PFL or peak and
signal present indicators. The mute LED illuminates when the
channel is MUTED.
14. PFL SWITCH
Allows the operator to monitor channel levels prior to the fader,
regardless of fader level or channel mute status. Used with the
input gain control (1) and peak indicator (15) and signal present
indicator (16) to accurately set input signal levels. With PFL
selected, the peak indicator(l5) will come on at half intensity.
15. PEAK INDICATOR LED (Red)
Illuminates 3dB before the onset of actual channel clipping and
is affected by the INPUT GAIN, EQ Settings, and CHANNEL
FADER settings. If any circuit is approaching overload, the LED
indicator will illuminate.
16.
SIGNAL PRESENT INDICAT.OR (Green)
Illuminates when input signal is above -3OdB. Green LED
indicator will vary in intensity with normal signal input variations.
17. CHANNEL FADER
Controls the level of the input channel to the Left/Right and
Mono outputs and any POST fader auxiliary sends. The fader
marking 0 is normal operating position, indicating unity gain
between input and output sections. There is an extra 1OdB
boost available at the fader which is obtained by raising the
fader to its full up position.
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Audio Owner Manual Section 2
MONITOR L
+6
+3
-0
-3
-6
-9
-12
-15
-18
-21
L R
L-J
PFL
EFX RETURNS
L R
I
PFL
FRONT PANEL CONTROLS
LEFT/RIGHT SECTION (Left is Shown)
References in ( ) are for Right Master
1. L(R) MONITOR METERS
These multipurpose meters monitor any source selected by the
Monitor section of the Master Module. When no switch is
selected within the monitor section, Left and Right outputs are
displayed. When any PFL switch on the mixer is engaged, these
meters automatically display the signal that is present at that
position. Ref level is +4dBv; range is from -2ldB to +6dB with
VU type response.
2.
EFX RETURN 1 (2), 3 (4)
These four returns allow mono line level signals (i.e. the output
from effects devices) to be added to the stereo mix. The l/4”
TRS Input jack can accept either -10 levels on the Tip or +4
levels on the Ring. Each ER( RETURN includes a LEVEL
control, BALANCE POT, and PFL.
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Audio Owner Manual Section 2
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El
MONO
L R
MUTE
STEREO RTN 1
PFL
FRONT PANEL CONTROLS - L/R CHANNEL (Cont)
LEFT/RIGHT SECTION Left is Shown
References in ( ) are for Right Master
3. STEREO RETURN 1 & (2)
The two STEREO RETURN inputs allow STEREO input signals
(i.e. the output of stereo tape machines or stereo effects
devices) to be mixed with the main outputs. The l/4”
TRS(stereo) jack accepts -10 levels; Left on Tip, Right on Ring.
Each STEREO RETURN includes a LEVEL control, AUX
SENDS A & B, a MONO switch which mixes Left and Right
input signals together, a BALANCE control, MUTE and PFL
switch.
4.
L(R) PEAK INDICATOR LED’
Illuminates 3dB before the onset of L/R clipping. Monitors both
the summing amp and fader amp for overload.
5. MASTER LEFT (RIGHT) OUTPUT FADERS
Controls the master level of the MAIN STEREO XLR outputs.
Normal position is at 0; 10 dB boost’is available if needed.
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Audio Owner Manual Section 2
12v
LAMP
B 1-j +48
D
PWRON
A
B
456
AUX MASTERS
STEREO OUT
MUTE
MONO OUT
1.
12V LAMP
BNC Connector to accept most of the popular goose neck
lamps to illuminate the mixer work area.
2. +46
Master power switch for 48 Volt PHANTOM POWER (for use
with CONDENSER microphones).
3.
PHANTOM POWER LED
Indicates that the Master Phantom Power switch is turned on
and phantom power is present in the mixer.
4. POWER ON LED
Indicates that power is on to the mixer. In the event that this
LED is not illuminated, check that the external power supply is
plugged into the mixer and the power supply is plugged into an
operational wall outlet.
5. AUX MASTERS A, 8, C, D
The master output level controls for auxiliary mixes A, B, C, and
D.
6. STEREO OUT
Master level control for an l/4” stereo output. Signal for this
output is derived from the stereo mix prior to the Master LeftI
Right slide faders (see USER OPTIONS) A.MUTE switch is
provided.
7.
MONO OUT
FRONT PANEL CONTROLS - MASTER
SECTION
Master level control of the MONO output. Signal for this output
is a mono sum of the stereo mix prior to the Master LefVRight
slide faders (see USER CONFIGURED OPTIONS). A MUTE
switch is provided.
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Audio Owner Manual Section 2
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AUX
A
0
AUX
B
AUX
C
AUX
D
1-1 MONO
I J
MONITOR
SELECT
@ PFL ON
SCEPTER
RACK
HEADPHONES
FRONT PANEL CONTROLS - MASTER SECTION (cant)
a.
MONITOR SELECT and LEVEL
This section selects the signal to the HEADPHONE OUTPUT
on the front panel and the MONITOR OUTPUT on the rear
panel. It also routes the selected signal to the LED Meter
section of the mixer. If no switches are engaged (and no PFL
LED illuminated), this signal is the LEFT/RIGHT output of the
console. When a switch within the monitor section is selected, it
automatically routes to the Headphone Output, Monitor Output,
and Meters. In the event that multiple switches are selected, the
switch closest to the BOTTOM of the panel has priority. When
ANY PFL switch is selected, the PFL ON LED indicator is
illuminated, and this signal has priority over any other switch
position. When illuminated, the PFL signal is present in the
Headphones, Monitor output, and visually on the LEFT/RIGHT
meters.
9.
HEADPHONE JACK
Accepts stereo headphones of 75. ohms or greater. Output
determined by the Monitor Select section. Headphone level is
controlled by the front panel control labeled LEV (Monitor
Level).
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Audio Owner Manual Section 2
MASTER
MASTER CONNECTIONS
0PIN 1 LIFT
PIN 1
LIFT
0,
Used to disconnect pin 1 from the MONO output connector.
Used to eliminate ground loops.
MONO BAL OUT
Male XLR-3 (Pin 2 Hot). Self Compensating Electronically
Balanced. Controlled by Mono Out Level pot. Normally
derived from mix of Pre-Fader Left & Right(See Options
Section). Nom level of +4dBv; Capable of +27dBv output
into 600 ohms or greater.
AUX OUT
A
0
AUX OUT
B
0
AUX OUT
C
Q3
AUX OUT
D
0
EREO
0
MONITOR
OUT
0
AUXAUNBALANCEDOUT
l/4” Jack. Controlled by Aux A Master. Nom level of +4dBv;
capable of +2ldBv into 600 ohms or greater.
AUXBUNBALANCEDOUT
l/4” Jack Controlled by Aux A Master. Nom level of +4dBv;
capable of +2ldBv into 600 ohms or greater.
AUXCUNBALANCEDOUT
l/4” Jack. Controlled by Aux A Master. Nom level of +4dBv;
capable of +2ldBv into 600 ohms or greater.
AUXDUNBALANCEDOUT
l/4” Jack. Controlled by Aux A Master. Nom level of +4dBv;
capable of +2ldBv into 600 ohms or greater.
STEREOUNBALANCEDOUT
l/4” Stereo Jack; Tip is Left, Ring is Right. Controlled by
Stereo Out Level pot. Normally derived from Pre-Fader Left
& Right(See Options Section). Capable of +2ldBv into 600
ohms or greater.
MONITOR UNBALANCED OUT
l/4” Stereo Jack; Tip is Left, Ring is Right. Controlled by
Monitor Level pot. Signal follows Monitor Select switch and
Auto-PFL. Capable of +2ldBv into 600 ohms or greater.
14

Audio Owner Manual
Section 2
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LEFT
__
EFX RTN
EFX RTN
3
STR RTN
1
Q L
INSERT
Q L
BUS IN
LEFT & (RIGHT) CONNECTIONS
PIN 1 LIFT
Used to disconnect pin 1 from the LEFT(RIGHT) output
connector. Use to eliminate ground loops.
LEFT(RIGHT) BAL OUT
Male XLR3 (Pin 2 Hot). Seff Compensating Electronically
Balanced. Capable of +27dBv output into 600 ohms or
greater.
EFX RETURN 1 (2) INPUT
l/4” Stereo Jack Tip accepts -10 devices, Ring accepts +4
devices
EFX RETURN 3 (4) INPUT
l/4” Stereo Jack. Tip accepts -10 devices, Ring accepts +4
devices
STEREO RETURN 1 (2)
l/4” Stereo jack; Tip is Left, Ring is Right. Normally accepts
-10 level Stereo effects devices or Tape Decks.
LEFT (RIGHT) INSERT JACK
l/4” Stereo Jack used to insert signal processing devices
into the Main outputs. The TIP connection is the SEND, and
the RING connection is the RETURN.
LEFT(RIGHT) BUS IN
l/4” Jack for inputing signals directly into the Main mix
amps. Used for stacking two mixers together.
-2dBv input level.
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