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Audio Owner Manual

Section 3

MASTER SECTION

 Lamp

This BNC Connector will accept 12 volt D.C. goose neck lamps rated at 50mA

to 

 current consumption. Used to illuminate the mixer work area.

Master power switch for 

 Volt PHANTOM POWER (for use with

CONDENSER microphones). When this switch is depressed, the LED will illuminate
indicating that power is supplied to any channel whose individual Phantom switch is
on.

Power on LED

Indicates that power is being supplied 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.

Aux Masters A, B, C, D

The master output level controls for auxiliary mixes A, B, C, and D. For

optimum performance (i.e. lowest noise), these controls should be set at 7 and the
individual channel sends should be set as high as possible.

Stereo Out

Master level control for the stereo output 

 jack socket. Signal for this

output is derived from the Pre-Insert stereo mix prior to the Left/Right faders. A
switch is provided to Mute this output when desired. Use this control when an
independent output is needed for a video or tape feed. Post-Insert and Post-Fader
selections are also possible.(see USER CONFIGURED OPTIONS section)

Mono Out

Master level control of the MONO output. Signal for this output is a mono sum

of the Pre-Insert stereo mix prior to the Left/Right faders. A MUTE switch is also
provided for this output. Post-Insert and Post-Fader selections are also

 USER CONFIGURED OPTIONS section)

22

Summary of Contents for SCEPTER

Page 1: ...SCEPTER 12 channel Rack Mount Mixer OWNER MANUAL Allen Heath Publication APO093 Issue 3 October 92 OWNER MANUAL...

Page 2: ...on 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...

Page 3: ...ns 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 acci...

Page 4: ...6 3 USE OF FACILITIES FRONT PANEL CONTROLS Input Channel Section 17 20 Left Right Section 21 Master Section 22 23 4 REAR PANEL CONNECTORS Input Channel Section 24 L R Section 25 26 Master Section 27 2...

Page 5: ...m System Block Diagram 7 SCHEMATIC DIAGRAMS Input Components and Option Placement Input Circuit Diagram Left Right Components and Option Placement _ Left Right Circuit Diagram Master Components and Op...

Page 6: ...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 nec...

Page 7: ...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...

Page 8: ...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 c...

Page 9: ...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 ahea...

Page 10: ...soft brush and a damp cloth Switches and potentiometers are lubricated for life the application of electrical lubricants to these parts is not recommended A number of user options are available These...

Page 11: ...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 Bala...

Page 12: ...ly better than 0 04 20Hz 20kHz at normal levels and gain settings 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 Out...

Page 13: ...ernal 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 w...

Page 14: ...he 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 ac...

Page 15: ...hin 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 4dB...

Page 16: ...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 to...

Page 17: ...t 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 lev...

Page 18: ...hen 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...

Page 19: ...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 N...

Page 20: ...eo 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 Nor...

Page 21: ...connect balanced low mic level signals into the channel LINE INPUT JACK Balanced l 4 stereo jack used to connect high line level signals into the channel Will accept balanced or unbalanced signals CHA...

Page 22: ...sing phantom power it is important to avoid connecting an UNBALANCED signal source to the MICROPHONE input without having first switched off the phantom power to that channel Input Gain Control The in...

Page 23: ...will change proportionally with fader movements and will be cut off when the mute switch is activated For this reason these mixes are normally used to feed external FX devices SCEPTER Series mixers ha...

Page 24: ...er In the up position a corner frequency of 120Hz is selected when engaged 60Hz is selected Eq In Switch This switch is used to activate the EQ section in the channel signal path When the switch is in...

Page 25: ...minates when channel audio signals approach overload The peak detection circuit samples the signal after the preamp after the equaliser and after the fader so revealing risk of overload at all stages...

Page 26: ...e ring contact Use the EFX PFL switch to help determine the proper position if not certain Stereo Return l 2 Two independent low level 1OdBV stereo inputs are provided for return tape or stereo effect...

Page 27: ...master output level controls for auxiliary mixes A B C and D For optimum performance i e lowest noise these controls should be set at 7 and the individual channel sends should be set as high as possib...

Page 28: ...s the selected signal to the Meters Headphones and Monitor Output The LEVel control sets the volume to the two outputs but has no effect on the meter In the event that multiple switches are selected t...

Page 29: ...is 20k Ohm balanced 1 Ok Ohm unbalanced Channel Insert Jack l 4 Stereo Jack used to insert signal processing devices into the channel The Tip is used for the SEND and the Ring connection is used for...

Page 30: ...o the Scepter L R mix By using the appropriate jack connection high or low level EFX devices can be accommodated The Tip of the jack is for low level 1 OdBV EFX devices 12dB gain is provided with this...

Page 31: ...unbalanced jack is used to inject signals into the Left Right mix amps Use this jack when stacking 2 mixers together This allows the Slave mixer outputs to get to the Master mixer without tying up in...

Page 32: ...pensate for the loss of the grounded pin Aux Out A B C D l 4 jacks unbalanced outputs of the Auxiliary buses Aux A B are normally set up as Pre EQ and are typically used to generate a stage monitor mi...

Page 33: ...ation or a performer mix for a keyboard player Output level is variable max output is 2ldBu into 600 Ohm or greater Tip is Left Ring is right The Headphone jack on the front panel follows the same sig...

Page 34: ...sis from the audio ground This is useful in rack mounting situations since the rack rails may be at a different potential than the audio ground This can cause ground loops By allowing the chassis to b...

Page 35: ...aster options Mono or Stereo Out Jumpers then the Rear panel DOES NOT have to be separated from the Circuit cards Eliminate step 2 and proceed as far as step 7 DISASSEMBLY Perform all work on a soft s...

Page 36: ...rews from each XLR jack 11 Lift the Rear panel off the circuit cards The Circuit cards are now accessible for changes to the jumper links or repair work If the main IDC 20 way ribbon harness is remove...

Page 37: ...EQ source select Pre EQ mute select 1 of 3 choices 1 of 3 choices for each Aux 1 of 3 choices 1 of 2 choices Direct Out Three choices are available for the Channel Direct Out Normally the Direct Out...

Page 38: ...and Mute Switch Used for Effect send Auxes C D default factory setting Pre EQ Source Select Three choices are provided for the Pre EQ source Normally the Post Insert Post HPF option is selected The a...

Page 39: ...lect both a Left and Right source the Aux will be a mono mix of the Stereo return 1 L R return Pre level Aux sends A B configured to follow the pre level mono mix of left and right return This is the...

Page 40: ...Post Insert if you want the MONO and STEREO OUT signals to be affected by any external processing equipment patched into the L R Inserts 3 Mono Out Post Insert Output is a mono mix of the main left r...

Page 41: ...ader Pre EQ X 4ux B Source Post Fader Pre Fader Pre EQ X 4ux C Source Post Fader X Pre Fader Pre EQ 4ux D Source Post Fader X Pre Fader Pre EQ Pre EQ Source Post Insert Post HPF X Post Insert Pre HPF...

Page 42: ...ound from the external equipment they are attached to In most rack situations there are a number of grounds tied together via the metal rack rails This can lead to ground loops which may cause hum in...

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