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MICROPHONE PREAMPLIFIER
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Instruction Manual
4. FUNCTIONS IN DETAIL
EXAMPLE OF USING PRE MODE
The FOH position has control over the 1788A’s but the monitor position doesn’t
want to be affected by the FOH’s gain changes.
In this case, the monitor position gets a fixed gain of 20dB from the microphone that
will not change. This represents a moderately amplified mic signal that is normally easy
to accommodate by the monitor mixing console. The Aux Output level can be adjusted
downward to reduce the Aux output level back approximately to mic level if necessary, but
you’re better off taking the hotter level and reducing your console’s preamp gain.
Note:
Pad, Polarity and Lo Cut
controls are in front of the variable gain amplifier
and will therefore affect the Aux Output in both PRE and POST modes. In the above
example, if the pad is suddenly engaged by the FOH operator, then a drop in level will
be seen at the Monitor position.
These are usually fixed settings that should be
decided upon during set up and left alone thereafter.
CHANGING THE PRE/POST SETTING
Remove the top cover and locate the jumper on each preamp module as illustrated below.
Move the jumper to the appropriate position.
JP1 JP2
PRE
POST
PRE
POST
INPUT
XFRMR
VR4
VR3
VR2
VR1
VR6
Default
Mic
Input
Main
Output
Selectable
26dB Pad
0 or -26dB
Input
Stage
POST
PRE
+20dB
Digitally
Controlled
Amplifier
0 to +39dB
1 dB stops
Output
Stage
+6dB
Main Output
Attenuation
0 to -27dB
AUX
Output
Output
Stage
+6dB
Aux Output
Attenuation
0 to -27dB
1 dB stops
1 dB stops
