I've got a nice Nad 3020a amp which has served me well over may years. recently it has developed a strange trait when turning on the power causing aloud buzzing noise through the speakers. Whilst this is mildly irritating in itself I am more worried about causing some damage to my beloved LS35A speakers. Whats more it seems to be getting worse - anyone got any clues on what could be causing this and how I might fix it?
Spud, the power caps are likely very dry and push along a very ugly voltage to the rest of the circuit. I would not use it until the very nice little unit has been serviced.
Most likely capacitors, either power supply or coupling variety. Take it to a repair shop and don't play it with any speaker you care to have intact until then. Or move on to a newer product with a warranty and better sound.
Disconnect all sources and see if it does it. Potentially one of your IC could have a bad ground...trust me, it's happened to me. If that doesn't work, go with the servicing.