I bought a used Peavey Bandit 112 80w combo for a song but it has a weird (to me) issue. When the tone pots of the guitars are all the way down, the amp makes almost no noise and plays fine. As the pots are turned up, though, squealing & hum gets louder & louder to the point of intolerable w/ tone at 5-10. I've used multiple guitars, multiple amps to check the guitars, multiple outlets & circuits. Also killed everything else that was plugged into the circuit to eliminate outside elec. interferance. Anybody got any ideas?

Certain kinds of hiss tend to go away when you turn down the treble, so does your overall presence. My guess is that you have an ungrounded wall outlet which just amplifies the above. More educated guesses should follow.

__________________
I reject reality and substitute my own

I kind of suspect that's part of it. We use a lot of different amps in the room & they could all make less noise but this particular amp is SO much worse than the others have been. The high gain input jack on this amp does nothing. Could that be a symptom?

What do you mean with could make less noise? I guess something's internally wrong if other amps don't make that noise but I can't help you with that I'm afraid.

__________________
I reject reality and substitute my own

I mean the other amps have a very small amount of hum & buzz sometimes, depending on effects & settings, but not not horribly obnoxious like the Bandit. Thanks for the input!

Does the amp make any of this noise with the input completely unplugged and you turn it up? If not the amp is probably ok. If you get a lot of noise when you turn up the amp with nothing plugged in then there is a problem with the amp, usually power supply filtration issues.

__________________
Stage Guitars: '80s Thin line LP Custom, '70 LP Standard, '83 Squier Black Headstock Strat w/ Dan Torres pickups, '59 Black Danelectro DC, sometimes others.

Pedal Board: Nady UHF 10 -> TU2 -> Rocktron Big Crush -> 70s MXR Phase 100 -> Cry Baby -> Bad Monkey -> Early '80s Rat -> Early '80s Ibanez CS 9 -> Ibanez DE 7 -> Behringer Dr 100 Stereo Reverb

Stage amps: '63 Blonde Tremolux w/ two original 2X10 cabinets with a '60 Ampeg Rocket/18 watt VTB Marshall clone/ Epi VJ into a Mashall 1965A