Allen&Heath Scepter USER GUIDE

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SCEPTER

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12 channel

Rack Mount Mixer

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OWNER MANUAL

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Allen & Heath

Publication:

OWNER MANUAL

APO093 Issue 3

October 92

ALLEN & HEATH

This product continues ALLEN & HEATH’s commitment to provide

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today’s audio business.

It brings you the latest in high

performance technology and offers the reassurance of over two

high quality tools engineered to meet the exacting requirements of

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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

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omissions. We also reserve the right to make changes in the

interest of further product development.

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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

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POWER UNIT

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model:

model:

I1

serial number:

serial number:

I1

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LIMITED ONE YEAR WARRANTY

ALLEN & HEATH BRENELL LTD.

This product has been manufactured in the UK by ALLEN & HEATH

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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

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original owner.
To ensure proper validation and handling of warranty services please

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return the WARRANTY REGISTRATION CARD,.

To ensure the high level of performance and reliability for which

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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

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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,

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neglect, or alteration other than as described in the Owner/Service Manual,

or approved by ALLEN & HEATH.

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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

A

Harman

TRlO 9LU

international Company

Allen & Heath

CONTENTS

1

......

INTRODUCTION

2

......

PANEL

3

......

USE

CONTROL

OF FACILITIES

.

General Information
Safety & Precaution
installation

........................................................ 3-4

User Service Information

Electronic Performance

DIAGRAMS

Input Channels

L/R

Section

..............

Master Section
Rear Panel

.............. .........................

.........................

..........................................

...................................

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.................................................

.........................................

........

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FRONT PANEL CONTROLS

Input Channel Section
Left/Right Section
Master Section

........

.......................

.............................................

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PAGE

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................14-16

................17-20

................22-23

1
2

5
6-7

8-9
10-11

12-13

21

4

. . . . . . REAR

5

......

USER

PANEL

CONFIGURED

CONNECTORS

Input Channel Section
L/R Section
Master Section

..............

.................................................

D.C. Power connector

OPTIONS

Access to Mixer Circuits

Options Descriptions

Direct Outputs

..................................................

Chan Aux Sends
Stereo Rtn Aux Sends

Mono & Stereo Output
User Options Table

Chassis Ground Isolation

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.*.a*

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................24

,25-26

27-28

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29

30-31
32
32
33-34

................34

35

.36

................37

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continued

Allen & Heath

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...

CONTENTS continued

6

. . . . . . SERVICE

7

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SCHEMATIC

INFORMATION

DIAGRAMS

PAGE

DIAGRAMS
Main

IDC

Ribbon Connector

Dimensions Diagram

. . . . . . . . . ..*......*......

System Block Diagram

. . . . . . . . . ...*

.,..*.*..*.....*..,...

Input Components and Option Placement..
Input Circuit Diagram

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Left / Right Components and Option Placement
Left / Right Circuit Diagram

...............

Master Components and Option Placement..
Master Circuit Diagram
EBOS Components

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&

Circuit Diagram...............

Power Supply Components & Circuit Diagram . .

..*...,.........

..*.....*.*..*..

. . . . . . . ...*.....

.......

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Audio Owner Manual

Section 1

INTRODUCTION

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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,

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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.

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Construction:

Aluminum front panel, stove enamel, enamel silk-screened legend.

1.

Steel Rear Panel and Chassis, grey stove enamel finish.

2.
Individual Channel assemblies secured to Front and Rear panels.

3.
Internal busbar circuits employ removable IDC harness.

4.

Glass-epoxy circuits cards for strength and reliablity

5.

All audio path

6.

7.

IC op-amp and discrete component circuit design.

ICs

are socketed for ease of service.

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

11 O-1 20V AC

AC

50/60

Hz 50VA Europe

50/60

Hz USA

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100 Volt AC 50/60 Hz 50VA Japan

NOTE:

providing

The MPS-8R power supply is provided as standard with the Scepter.

+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.

1

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

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Section 1

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INSTALLATION

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

unit, power supply and other items are correctly repacked to avoid transit damage.
Please ensure that the fader knobs are in the up position.

the local supply.

Scepter unit. Ensure that it latches firmly.

Earthing/Grounding in the audio system

system is well earthed (grounded).

should you need to ship the unit in the future. Please ensure that the Scepter

Check that the AC operating voltage marked on the power unit is the same as

Connect the DC power cord from the power supply into the rear panel of the

There two important reasons why it is necessary to ensure that your audio

Safety - prevention of electric shock (see previous section on SAFETY)

1)

Shielding - preventing external electrical interference from causing noise in the

2)

audio signal path.

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

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be formed. This usually results in an excess hum in the system, but can also cause
the breakthrough of RF and other noises.

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

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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

Alternatively; just one piece of equipment, usually the power amplifier, is

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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

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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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3

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.

4

Audio Owner Manual

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Section

1

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USER SERVICE INFORMATION

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

ELECTRONIC PERFORMANCE

Section 1

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
LINE IN to

L/R

to Mono Out

L/R

L/R

FX RETURN to

INPUT PAD

,.., ,,,.........I*.........*.

Out

Out

..,.,.

L/R

..a.....,.... ,,,......................

+80dB

. .

. . . . . . ..*..........*....*

. . .

..**......*.......s.*.

Out . . . . . . . . . . . . . . . . . . . .

+62dB
+1 OdB

+24dB

-16dB

INPUT GAIN CONTROL RANGE......52dB

.*.............**...*.....***...

FREQUENCY RESPONSE:

Equalizer set to flat response or switched out

INTERNAL OPERATING

ALL OUTPUTS AND INSERTS IN-PHASE REF TO XLR PIN 2 INPUT
AND

l/4”

TIP CONNECTOR.

LEVEL=

. . . ..*......**............*

. . . ..*...*..............*

. . . . . . . . . . . . . .

Channel=

70dB with Pad

20Hz

to

OdBu;

20kHz +0/-l

L/R= -2dBu

dB.

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 =

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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:

6

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+a

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Audio Owner Manual

ELECTRONIC PERFORMANCE continued

THD typically better than 0.04%

20Hz-20kHz at ‘normal levels and gain settings

NOISE PERFORMANCE:

L or R
L or R

Aux

Output(all

Output(1

input @ unity gain)-83dBu

Outputs(Unity gain)-90dBu

Microphone Input equivalent noise-l 27dBu (200 Source)

Section 1

RMS noise 20kHz bandwidth

input faders closed)-83dBu

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7

Audio Owner Manual

LINE

FRONT PANEL CONTROLS.

INPUT CHANNEL

GAIN

1.

Adjusts the gain of the input pre-amplifier to suit input levels.
Control range is

+18

to

+66dB

(mic) and -4 to

+43dB

Section 2

(line).

L-J

AUX SENDS

HF

-0+

PAD

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LINE

2.

Selects between Microphone and Line input sources. With the
switch engaged, Line input is selected.

PAD

3.

When selected, reduces the input signal level by approximately

16dB.

4.

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)

5.

HIGH FREQUENCY EQUALIZER

Boosts or cuts the High Frequencies by up to 16dB at the

corner frequency of

6.

MID FREQUENCY SWEEP CONTROL

Selects the center frequency affected by the mid frequency gain

control. Continuously variable from 250Hz to 6

1OkHz

with Shelving characteristics.

kHz.

MID - ?

III

+

E

EQ IN

7.

MID FREQUENCY EQUALIZER

Boost or cuts the Mid Frequency by up to 12dB. Approximately
1 octave around the center frequency with Peak/Dip

characteristics

6.

LOW FREQUENCY EQUALIZER

Boost or cuts the Low Frequencies by up to 16dB at the corner

frequency selected by the Low Frequency Select Switch.

9.

LOW FREQUENCY SELECT SWITCH

Selects the corner frequency of the Low Frequency Equalizer
between

10.

EQ

With this switch engaged, the EQ section is active in the
channel. With the switch released the EQ section is bypassed.

IN

12OHz(Up)

and

8

GOHz(Down).