Why does my guitar amp blow every speaker it comes in contact with?
March 27, 2010 9:53 PM   Subscribe

Can a guitar amplifier ruin every speaker cabinet it gets plugged into?

I bought a second hand solid state marshall head for cheap. It worked fine for a while. Then one day I turned it on and the speaker made a really loud popping noise and crackled like crazy. Every time I tried to turn it on thereafter the same thing would happen almost instantly, even with all of the gain/volume controls at zero. I was pretty sure the speaker had blown and not the amp, because I recall removing the head from the equation and the same thing happened while using the original cabinet.

Thinking the amp was fine, I attempted to sell it on craigslist. A buyer came over, plugged his own guitar/cabinet in, and it happens again. All knobs at zero. I ended up giving the amp away for free (I bought it for almost nothing anyways), and now I am worried that it destroyed his cabinet as well.

Could it be that the amp is toast, and it blows every speaker it comes in contact with? Cursed thing...
posted by nurgle to Technology (2 answers total) 1 user marked this as a favorite
Sure sounds like it.

Consider the case where the volume control pot is noisy; it usually sits between the pre-amp (where your input gain, tone controls, effects, etc are) and the power amp. Any noise from the pot onwards is fed though, unattenuated, to the power amp which runs at a fixed gain. Crackling noise especially is bad; that tends to dislocate speaker coils.

Or say the final drive stage of the power amp is stuffed. Not so bad in valve amps, because they've almost always got an output transformer (which won't pass DC - it just gets hot), and 90% of the time the valves go open-circuit anyway. However, 90%+ of the time in solid state amps the final stage goes short-circuit - putting the full amp supply rail across the speaker coil. That too will usually either dislocate, or straight-up burn out, the speaker coil.
posted by Pinback at 10:26 PM on March 27, 2010

Response by poster: How awful. Hopefully that guy doesn't come back here and beat down my door...
posted by nurgle at 10:34 PM on March 27, 2010

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