STAM AUDIO ENGINEERING
12. Adjust R79 (Rev G Output level fine adjust) to match Rev A and D levels
13. Adjust R75 for minimum 2nd harmonic magnitude.
14. Double check your levels are matched by switching between A, D ,G revisions. Repeat
the procedure if necessary
Q-bias
With the same settings used for level calibration do the following:
1. Switch to Rev A
2. Set Attack and Release pot all the way CW
3. Adjust R59 CW until you see a drop in your output level level. Then turn R59 the
opposite direction while watching your level meter. It may take several turns to see a
change. The goal here is find the point where the output level stops increasing thereby
moving the FET out of its conductive range. Once you have verified there is no more
level increase turn R59 in the opposite direction until the output level drops 1dB. You
have just biased the FET to the start of its conductive range.
VU Meter calibration
After the Q Bias calibration you can move to VU meter adjustment and GR tracking procedure.
Changing the order of the calibration procedure steps may lead to wrong results.
1. adjust R155 until the meter reads zero. CW moves the meter up on the scale
2. Getting the VU meter to accurately track GR
involves many small adjustments between
the meter zero adjustment (R155) and the tracking adjustment (R154).
3. Apply a +4dBu 1kHz signal to the input.
4. Bypass compression and set Attack and Release pots full CW.
5. Set the Input pot to 12 o’clock. Set Output pot for unity gain on your metering system
(+4dBu)
6. Engage compression by pressing the 20:1 ratio. Watch for a level reduction on your
metering system. You want to match the gain reduction on the GR Meter to what is seen
on your metering system by adjusting the tracking adjust trimmer, R154.
SA-76 ADG - USER MANUAL
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