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Audio Owner Manual

Section 4

LEFT   RIGHT CHANNEL CONNECTIONS

Pin 1 Lift

This recessed switch is used to disconnect Pin 1 from ground on the LEFT/

RIGHT output XLR connectors. Used to eliminate ground loops when connecting up
different pieces of equipment Use a pencil or other thin probe to activate the switch;
Pin 1 is lifted when the switch is IN.

Left/Right Main Outputs

Main outputs for the Left and Right mix amps. These XLR connector outputs

follow the 

 faders. Their outputs can be monitored on the L/R LED meters. 

balanced XLR. Pin 2 hot, Pin 3 low, Pin 1 ground. Output impedance 

 Ohm,

nominal level 

 maximum level of 

 balanced, 

 unbalanced.

These outputs are self-compensating electronically balanced. They can be operated

unbalanced with either polarity, by taking the signal from the desired pin 
phase; 

 and connecting the unused output pin to ground. The output of

the driving pin will increase by 6dB to compensate for the loss of the grounded pin.

 

 stereo jack for returning effects back into 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 

 EFX devices; 

gain is provided with this connection to bring the output level of the device up to

 For high level 

 EFX devices, use the unity gain Ring connection

either by inserting the plug half way in or by wiring the plug using the Ring
connection instead of the Tip. Input impedance is 25k Ohm for low level, 
Ohm for high level.

Stereo Return 

 stereo jack for returning stereo EFX, Tape, CD or other low level stereo

sources into the Scepter. The jack is wired for low level 

 inputs; Tip being

Left input and the Ring as right. Input impedance is 

 Ohm in stereo mode,

dropping to 20k Ohm when the MONO switch is pressed(Tip   Ring inputs are
mixed thru 1 Ok Ohm resistors with MONO). Aux A   B pre-level sends are available
for wet monitoring.

L/R Insert

 Stereo Jack used to insert signal processing devices into Left or Right.

The Tip is used for the Send, and the Ring connection is used for the Return. The

insert point is located after the mix amp just before the fader. Nominal signal level is

 output impedance is 50 Ohm with a recommended load of 600 Ohm or

25

Содержание SCEPTER

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

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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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