Hi, thanks for your response, I really appreciate it. You're right, that would be 50 Hz
, I'm in Yurp.
It's more of a white noise. There is some hum, but it's very much in the background and only if you crank it up very loud, so I don't consider that a problem. The hiss increases if you switch on the tweeters, and can influenced with the eq.
I know it's difficult to diagnose from thousands of miles away, so I'm hoping for some general hints on where to start looking. After a lot of googling I'm tempted to check the resistors around the transistors, and maybe replacing them (film resistors are supposed to generate less noise, if I understood correctly)
If someone knows a place for the schematics, that would be a great starting point. I found a schematic that resembles the configuration of this amp on the Rickenbacker site: the TR35B. Could anyone confirm that it's similar, if not the same (at least in the preamp and power supply parts?)