User Manual

The Technical Stuff
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26
“Q” Bias
The compression threshold is set using R59. Under normal circumstances, this control does not need
to be adjusted. The threshold is dependent upon the specific characteristics of the VVR FET (Q1), and
it will be necessary to re-adjust it if Q1 is changed.
The following procedure is used to set “Q” bias:
1. Select either +4 or +8 output metering.
2. Adjust R59 fully counterclockwise (CCW).
3. Apply a sine wave signal to the 1176LN.
4. Adjust the Input and Output controls for 0dB output.
5. Slowly adjust R59 CW until the output decreases by 1.0 dB.
Meter Driver Null
A multimeter is needed to perform this calibration procedure:
1. Disconnect any input and output connections on the 1176LN.
2. Set your multimeter to measure DC volts.
3. Depress the Meter GR pushbutton.
4. Adjust the Zero potentiometer R71 (  see page 25) so that the meter reads near 0 dB.
5. Connect the multimeter across R74.
6. Adjust R75 for a minimum voltage reading.
7. Disconnect the multimeter.
8. Readjust the Zero Set potentiometer R71 so that the meter reads 0 dB