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What might be causing this slight buzzing coming from the left channel speaker? It increases in volume when I turn up the amp until it is at full volume and then the buzzing stops. This is when there is no input or music playing.The buzzing does not get in the way of the music and I can barely hear it from my listening seat. The speakers don't seem to matter, I've tried 3 different sets of speakers all with the same result.
I have cleaned the volume pot with DeOxit and have switched all tubes, all to no effect.
Thanks for any advice.
Follow Ups:
Dave
Did you change out the selenium that provides filament and neg bias for the tubes? Even tho is doesnt seem to buzz in one channel,I find this to be 90% of a lot of problems with what you are describing.Check your filament voltage on the 12ax7s at pins 4 and 5 and see if you have 12.6vdc.If you have like 10v or so,change the selenium and filter cap with it.
As Mike said, oft-times a power supply problem does not manifest itself equally in both channels as would seem intuitively. Perhaps the electrical potential is least in one than the other by a minute amount & that is why one channel bears the brunt. I do not actually know the reason, but do know such can exist & that electrical potential can be what the electricity decides, not what we would always like. Good Luck.
Thanks all for your advice. Yes, I have tried switching around all the tubes and the buzzing remains in the left channel. I guess I'll have to check the caps as suggested.Thanks,
Dave
Hi,You may need to swap your 6BL8 or 6U8 tubes between channels. If the buzz follows the tube, so tube on left channel need to be replaced.
I have experienced the same problem with my 299C and it works.
I took his statement that he switched all tubes to mean such has already been tried (switched = swap in this context).
If so I would suspect a leaky cap in the line preamp section.
--
Al G
Born To Tinker!
And by leaky, he means leaks Direct Current (not leaks liquid or wax). Measure the output of the capacitor for DC voltage to discover if this is occuring.
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