C-4 Pre with HF Oscillation

Thanks to Avionic's suggestions, I replaced the 47uf/50v Nichicon KA caps in the +/- 30 volt regulator with Nichicon 47/50 KL caps and the oscillations went away. I now have a clean +/- 30 volts.

I did a little experimenting while I was doing it and found that if a KA was in one position and a KL in the other, no oscillations occurred. Only when both positions used the KA caps would it oscillate. Some aspect of those KA caps must have changed the feedback just enough to cause the stage to oscillate. After replacing the caps I replaced all of the VD1212 diodes.

I have it back in my system (with an M-4) after several years absence, replacing an Adcom GFP565 and, to me, it blows the Adcom away.

Thanks everyone :thmbsp:
 
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