Harsh cyclic hum coming from amp?

Discussion in 'Gear & Equipment' started by PuriPuriPrisoner, Mar 4, 2019.

  1. PuriPuriPrisoner

    PuriPuriPrisoner SS.org Regular

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    I got a triple rectifier in the mail last week. I noticed that there was a high pitched rattling hum coming from the tubes so I assumed they were on their way out. Here's a link to video showing that noise:
    .
    Today, a new noise started where a harsh cyclic hum was coming out of the speakers. Here's two videos of that noise:

    and

    I was trying to get a partial refund from the seller because he didn't mention that the tubes were bad. He said that the noise wasn't happening when he had it and he opened up a shipping damage claim with reverb. Should I just return the amp? I like the amp but I'm not sure if this is coming from bad tubes or damaged internals.
     
  2. PuriPuriPrisoner

    PuriPuriPrisoner SS.org Regular

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    Whoops. Sorry for the formatting of this thread being all fucked up. I didn't know it would change the links into full video blocks. I'll try to fix that now. Also I wanted to mention that the cyclic wasn't happening early today. It kinda just started happening out of the blue. I turned on the amp, took it off standby, and cranked the volume. I tapped all the tubes. The power amp tubes didn't make any noise but the the two left most preamp tubes were noticeably louder than the others. I guess I'll just replace those and see if that fixes my issues.
     
    Last edited: Mar 4, 2019
  3. DudeManBrother

    DudeManBrother Hey...how did everybody get in my room?

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    Once the tubes have cooled down, make sure they’re all fully seated. If you have some deoxit or other small component cleaner, maybe give a quick spray in the tube sockets. It sounds like you have already found two potentially microphonic tubes, so that’s the best place to start.
     
  4. mnemonic

    mnemonic Custom User Title

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    The physical noise from the head may just be mechanical noise from the transformer. I get some slight mechanical noise from my dual recto power transformer but unless I’m in a dead-quiet room and right on top of the amp, I can’t really hear it. Try putting your hand on top of the power transformer and see if it changes in volume, pitch, etc. At least on my dual, I think it’s mostly some slight resonation of the end-bell.

    Loose mounting screws will also contribute to vibrational noise.

    The second and third videos, I assume you’re not using any other outboard gear like effects in the loop or in front of the amp? Try guitar > cable > amp > speaker cable > cab, to limit variables, if you haven’t already. Also try a new cable, new guitar, etc, just so you can ensure it’s the amp. I’ve had bad cables make similar noises. In fact my dad thought his amp broke last week because of some horrendous ground noise, it was a busted cable.

    Try flipping though the various options to see if it disappears, for instance loop hard bypassed or on, tube Rectifier or solidstate, etc.

    After that you can try cleaning out the various sockets and jacks with contact cleaner (good to do with new gear anyway). It could be a bad preamp tube, it happens. Try swapping in a known good preamp tube one at a time to see if you can find a culprit.
     
    protest likes this.
  5. LeftOurEyes

    LeftOurEyes SS.org Regular

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    You're not even sure yet what the problem is but already requesting a partial refund lol. This kinda stuff is what makes me not want to ever sell stuff online. I don't know what some people expect when buying used gear, tubes go bad sometimes...
     
    efiltsohg likes this.
  6. PuriPuriPrisoner

    PuriPuriPrisoner SS.org Regular

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    Well when you advertise the amp as having newer tubes, I'm gonna be a little pissed when the amp has tube noise.
     
  7. LeftOurEyes

    LeftOurEyes SS.org Regular

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    You should find the problem before requesting money back, simple. You're not even for sure yet what it is.
     
  8. sharedEQ

    sharedEQ SS.org Regular

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    It needs a cap job. Ive had that noise before and done the cap job myself. Totally silent afterwards. The amp I did the caps on was only ten years old; they can go prematurely bad, aren't usually expected to last more than 20ish years but can go longer.


    If the power amp makes noise with a volume off guitar direct into the FX return, that means the amp is making that noise, it cant be fixed by a noise gate or new tubes.

    Job will cost several hundred dollars. Capacitors are usually around $50-75 if you do the work yourself. BTW, caps don't just go bad from shipping damage. Its something that develops over time, can actually happen faster if the amp is not played much.

    I would return it based on undisclosed damage. You may need to take it to an amp tech to get it documented so you don't eat return shipping. What an Ahole seller.
     
  9. BlasphemyMadeFlesh

    BlasphemyMadeFlesh Line 666

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    Tubes can move in travel; sometimes taking them all out and putting them back in will solve some issues. I recently sold a Mark IV and upon arrival the buyer had to take the preamp tubes out and seat them again because channels weren’t switching. Worked perfectly fine before I sent it.
     

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