Audio Developments AD144 - Manual (Page 22)

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For optimum performance at line level, the stereo module employs RFI suppressed,
double-balanced, instrumentation-grade input amplifiers.
The input-changeover toggle (1) interchanges the inputs to connectors 1 & 2 without
having to replug. The phase-change toggle (2) changes the phase of the signal on
connector 2 and is unaffected by the position of toggle (1).
The module's input stages have fixed, unity gain; nevertheless it is possible to
rebalance the stereo input-signal with the OFFSET control (3). (±10dB variation).
Equalisers identical with those of the microphone/line module may be inserted in both
left and right signal paths via EQ selector (16). The high-, mid- and low-frequency
amplitude controls are ganged, operating simultaneously on both equalisers.
Auxiliary attenuators (7) to (10) and source switches (17) to (20) are identical with
those of the mic/line module. A mix of the left and right signal paths is used to drive
the auxiliary sends.
When an input is in the M-S domain, the width may be altered by the OFFSET
control (3) and the signal then decoded to the L-R domain by L/R - DEC (21).
For a stereo picture the MON/ST potentiometer (11) will be fully clockwise;
counter-clockwise rotation will gradually reduce the width of the picture to mono,
presenting the M-input signal (only) to the L&R outputs from the module by reducing
the ambient content.
When an input is in the L-R domain, the following paragraph describes how to perform
a mono reduction. BUT, compare such an operation with the M-signal after
converting to M-S by L/R - DEC (21)… Because of phase cancellations a
L+R=MONO has less ‘vitality’ than the equivalent M extraction.
Routeing buttons (12) A/B and C/D route the channel stereo signal to outputs A &
B and/or outputs C & D. L routes the LH input signal to both A and B outputs;
similarly R routes the RH input signal to both A and B outputs; L AND R routes a
mix of the stereo signal to both A and B outputs - for these mono capabilities, A/B
must also be selected, (C/D remains an independent routeing to C and D outputs).
Stereo PFL (13) overrides any other signal on monitor 2 output.
MON (22) is identical with MON on the mic/line module.
Should LEDs (14) - red=left, green=right - indicate overload, the channel should be
checked for excessive equalisation. If this is not the cause of overload, the signal to
the channel should be reduced in level. The LEDs illuminate at 3dB before clipping at
the input to the stereo fader.
The stereo Penny & Giles fader (15) is calibrated 10dB down from its fully open
position, allowing the operator to work with 10dB of gain in reserve.