All great suggestions. One other possibility could be too high gain combination between the preamp and the amp. My (tube) preamp has a separate output gain control - in addition to volume control, and I can increase the gain to the point where I can hear buzz/hum from the speakers. Preamp gain and amp input sensitivity mismatch can cause this too if there's even the slightest ground noise.
Question about hum from speakers
I know there's at least one amp engineer here... I'd like some help. I bought a used solid-state amp from ebay; the ad read "
McCORMACK POWER DRIVE DNA-.5 Deluxe REV B POWER AMPLIFIER - EXCELLENT CONDITION!"
Well, I swapped it in, replacing a Dynaco Stereo 120, and there's a hum from both speakers. I have to believe that the seller was well aware of the hum. What I'm wondering is, is the hum a result of some electronic component(s) in the amp failing (or having failed), such that it's salvageable by replacing the bad component(s)? Or would that be hoping too much?
Well, I swapped it in, replacing a Dynaco Stereo 120, and there's a hum from both speakers. I have to believe that the seller was well aware of the hum. What I'm wondering is, is the hum a result of some electronic component(s) in the amp failing (or having failed), such that it's salvageable by replacing the bad component(s)? Or would that be hoping too much?