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Riddle me this: my loud amp, a peavey musician iii, seems to make a noise like that of a blowing wind when it gets hot. Happens regardless of what is or isn't plugged into the input. One day I left the amp in my car on a hot day and it made the noise within the first hour of practice. Today it hadn't been in the heat and it took about 3 hours to make the noise.

Any guess what would cause this? Just dusty something or other?

Something's drifting out of spec with the heat.

Try changing the caps. Old and leaky caps often sound hissy. Cheap and easy Job.

Thanks! I'll put new caps in. Hopefully that's it.

It's funny, I have a beat to shit mk 4 that exhibits almost the exact opposite behaviour. Fire it up cold and it'll spit all manner of noise at you, then it calms the fuck down once temperatures stabilize (5-10 minutes or so).

Since yours is taking a really long time to reach "failure" mode, I would suspect components that are not in the heavy lifting stages (power supply and output devices) since those reach temp fairly fast. It could be a bias resistor, or leaky cap, or poor solder joint in the preamp section as well. 3 hours is a long time to wait for the symptom to surface, and it would not surprise me if it's trapped ambient heat (inside the case) that triggers it - which would translate to the problem not surfacing while the amp is open for servicing.

If you self perform the work, I'd recommend going at it with a heat gun to aggravate localized sections so you don't waste hundreds of hours chasing your tail.

Same happens to my mark iv 400 after 1-2 hours of usage, but it's more like a buzz, a fucking loud buzz that I actually like, I wish it could be sent to the speakers.

crochambeau wrote:It's funny, I have a beat to shit mk 4 that exhibits almost the exact opposite behaviour. Fire it up cold and it'll spit all manner of noise at you, then it calms the fuck down once temperatures stabilize (5-10 minutes or so).

Since yours is taking a really long time to reach "failure" mode, I would suspect components that are not in the heavy lifting stages (power supply and output devices) since those reach temp fairly fast. It could be a bias resistor, or leaky cap, or poor solder joint in the preamp section as well. 3 hours is a long time to wait for the symptom to surface, and it would not surprise me if it's trapped ambient heat (inside the case) that triggers it - which would translate to the problem not surfacing while the amp is open for servicing.

If you self perform the work, I'd recommend going at it with a heat gun to aggravate localized sections so you don't waste hundreds of hours chasing your tail.

this heat gun suggestion is one of the best things I have ever read, would never have thought of that,