02-19-2014, 08:28 PM
Ron, I don't think the differences in voltages are significant with regard to the low audio issue. One channel is a few volts high, the other a few low, but not really out of the ordinary. This balance issue really does not affect the AC gain of the amp. Otherwise the voltages look reasonable with regard to biasing of the individual transistors.
On thing that will affect the AC gain is the driver feedback bypass cap C26. This cap reduces the AC feedback from the driver stage collector, preventing loss of AC gain while maintaining the DC feedback. If this cap is open, It will reduce the AC gain, which may cause the low volume. You can try bypassing it with the 100 uF cap you have and see if it makes a difference.
Electrolytics are always suspect, so this is where I would look first.
On thing that will affect the AC gain is the driver feedback bypass cap C26. This cap reduces the AC feedback from the driver stage collector, preventing loss of AC gain while maintaining the DC feedback. If this cap is open, It will reduce the AC gain, which may cause the low volume. You can try bypassing it with the 100 uF cap you have and see if it makes a difference.
Electrolytics are always suspect, so this is where I would look first.
