My amp is squealing and popping

Discussion in 'Amplifiers' started by NBW, Oct 15, 2021.

  1. NBW

    NBW New Member

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    It’s occasional and annoying. The amp in question is a Gibson RV Super.
     
  2. WEDGE

    WEDGE Zombie five, DFZ

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    Tubes? Guessing not many on here are fluent on Gibson amps past general knowledge.
     
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  3. LSchefman

    LSchefman Hears Tones

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    Squealing and popping is usually a microphonic preamp tube. Not always, but often.

    If you tap on the tubes with a chopstick or pencil, with everything unplugged from the amp, and you hear tapping loud and clear from the speaker when you tap one of the tubes, it's that tube. All you have to do is replace it.

    Note, however, that sometimes you hear some tapping when you tap on the v1 preamp tube (the one closest to the input). That's normal, unless it's quite loud.
     
  4. NBW

    NBW New Member

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    This is exactly the kind of advice I need. I think I put in a matched set of power tubes not that long ago and I was hoping that wouldn’t be the issue.
     
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  5. LSchefman

    LSchefman Hears Tones

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    I hope to heck I'm right! But you'll know once you do the tube tapping thing.
     
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  6. RickP

    RickP Established 1960, Still Not Dead

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  7. SinSir

    SinSir Mad Scientist

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    I just had a similar issue from a set of power tubes I picked up. Rattle and popping, no squealing. Swapped back to old tubes and problem went away. Haven't diagnosed any further yet.
     
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  8. RickP

    RickP Established 1960, Still Not Dead

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    It might be in the power section, you never know, but it’s the squealing in particular the hints at a preamp tube. It’ll make that noise, often, with a guitar even plugged in. I’m curious to see!
     
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  9. SinSir

    SinSir Mad Scientist

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    I agree. Initially it freaked me out a little bit, more so the girlfriend with the pop. Part of my troubleshooting 101, I trace back to the last thing done and go from there. I do think I have a preamp tube issue as well. In my case I'm wondering if the new tubes amplified the issue.

    Thanks for the useful link!
     
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  10. Going Modal

    Going Modal I should be practicing right now.

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    Les is correct about checking for microphonic preamp tubes with a wood pencil, chopstick, or wooden spoon, etc. However I've also recently had some power tubes going bad, which resulted in some crazy squealing & intermittent cutting-out. I peeked around back to see one of the two power tubes glowing purple-red in a way that didn't look good. Turned it off right away, then changed the power tubes... all better now.
     
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  11. DISTORT6

    DISTORT6 NJ Devil

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    I can vouch for getting whacked with a wooden spoon. They were my mothers weapon of choice.
    I’m a survivor.:D

     
  12. Going Modal

    Going Modal I should be practicing right now.

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    You, too, must have gone microphonic!!!
     
  13. DISTORT6

    DISTORT6 NJ Devil

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    HAHAHA!:p
    Yup. Hence the spoon. Problem fixed.
     
  14. LSchefman

    LSchefman Hears Tones

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    Yup. Tube amps are pretty simple beasts. First thing to do is check the tubes.
     
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  15. NBW

    NBW New Member

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    After tapping on stuff I think it’s the phase splitter. This amp has a ton of 12ax7s - 5 of them and two 12at7s. I just ordered a bunch of JJs as they are inexpensive and apparently came stock. It is an amazing and somewhat idiosyncratic amp.
     
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  16. NBW

    NBW New Member

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    Well I was wrong. I replaced all the pre amp, effects loop and reverb tubes. It was still popping. Then I looked into the power section (the front panel was off) and I could see one of the el84s glow super brigh and the it would pop as it discharged.

    that was one of a matched set of JJ el84s I installed not too long ago. I put the Mullards that came in the amp back, which cured the pop, but now it’s noisy (probably why I retubed it.
     
  17. LSchefman

    LSchefman Hears Tones

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    New Mullards are just re-branded Sovteks. With an EL84 amp tube matching is less important. I'd just put the working JJs back in, and buy another JJ. For new tubes (as opposed to NOS), they're usually pretty good.
     
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  18. NBW

    NBW New Member

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    I think the Mullards have lower output and somehow worse shielding. I just ordered another JJ el-84 so I’ll put those back shortly.
     
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  19. LSchefman

    LSchefman Hears Tones

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    I'm an NOS person, so, yes, kinda spoiled on very good, classic tubes. However, IMHO of the current tube offerings, JJ are perhaps the least problematic.
     
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  20. NBW

    NBW New Member

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    Seems like it’s fixed now. Sounds fantastic again.
     
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