I recently acquired a SOB amp, which sounds great and works fine other than it has developed a crackle through the speakers when it is turned off. Anyone experienced this or can point to a likely cause?
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Anonymous
Do you turn off/stop the source of music first?
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tubehifi
This is most likely caused by a tube that is getting old.
Bruce
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Anonymous
Thanks Bruce, that was my first thought. I work away from home, but will be back tomorrow, will measure some voltages and see what’s what.
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Anonymous
wrote:
Do you turn off/stop the source of music first?


Yes.
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Anonymous
Just to round this out, got up this morning and decided to start swapping the 509’s between channels as a quick check, started with the two outside valves. Amp powered up and then BANG through left speaker ( noise was on the left side originally). Checked fuses and outer left was blown, which meant it had to be the second from the left 509 that was the culprit. Replaced that and the fuse and now all is well. :-)
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Anonymous
Ouch!

glad it's sorted
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Anonymous
Thanks, me too. :-)
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