Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: uki on September 28, 2017, 11:24:07 am
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Hey guys !!
My 50watts amp is making some unwanted noises, been playing a lot with this amp in the last 3-4 years it is small and easy to carry around, seen like it is tubes related, when playing hard the guitar, a noise happen and sounds like something is loose and vibrating and a whistle like also, so i decided to check out the tubes, replaced one by one the pre amp tubes, v2 did the trick with the whistle, replaced the stock Sovtek tube with a JJ(ecc83), then removed the power tubes(el84 el34s) one by one, tested with 3 tubes then 2, then one, and tested each tube separated, with every single one of the tubes, the loose noise still happening, also is possible to hear in the power tubes while out of the amp something loose inside of it with a little shake, could it be the source of the noise?
(I don't have any extra el84 el34s)
fixed, el84 not el34
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It's not a great idea to run it with 3 EL34s installed because the output tubes are supposed to work in balanced pairs (if you removed 2 it would also be good to know you're removing one pair and leaving the other, instead of removing 2 from the same "side" and leaving the opposite).
Anyways, it does sound like a bad tube-- or at least something is microphonic. Does the amp have reverb? Reverb springs are another candidate for picking up vibration.
"Whistling" might suggest oscillation, which is a completely electrical problem. Microphonics tend to be a problem when playing specific notes (but not others) and sound more like "ringing" or rattling.
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Yes it does have reverb, but even with the reverb off, the noise was present, i got new tubes, problem solved !
I did beat the old tubes a lot, all of them are no good, the amp sounds way way better now with the new ones, better tone and no noise !