Quick fix Vintage Dyna Dynaco PAS tube type preamp repair Channel hiss distortion

If you are experiencing a strange hiss or distorted audio from your Dyna preamp, the first thing to check is the Left & Right audio output RCA jacks for stray DC voltage. Normally you should only see a small mv level. If you see a few tenths or perhaps full voltage level on the output, you have a leaky coupling cap. That DC voltage is going right into your amplifier inputs! locating the caps is pretty straight forward referencing the schematic. Always bump the capacitor rated voltage up to 600v. Dynaco used 400v caps, however the plate voltage is around 450! So, those old originals are under some stress. Yes, a full cap job is always a good idea. However, I perform what the customer wants.