Pickups literally vibrating and feeding back

Discussion in 'Luthier's Corner' started by PermissionToLand, Jan 25, 2021.

  1. PermissionToLand

    PermissionToLand Well-Known Member

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    So I've had this issue with two guitars now (both have open coil humbuckers) where at high volumes during practice, the pickups will literally vibrate and feedback. Pressing on the pickup to hold it in place prevents it. Weirdly, it only seems to be the bridge pickups doing it, which if anything should be held tighter in place because it's set higher and therefore compressing the spring more. Any ideas?
     
  2. donepearce

    donepearce Well-Known Member

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    Wax potting is the answer to this. You should be able to find a guitar tech near you who can do it for you. It locks everything inside the pickup solid (you can still adjust the polepiece screws) and nothing vibrates.
     
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  3. DrBGood

    DrBGood Well-Known Member

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    And then raising pole pieces is fun, you have that wax coming out ... cool !
     
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  4. PermissionToLand

    PermissionToLand Well-Known Member

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    It's a Seymour Duncan A2 Pro, which is supposed to be wax potted according to SD.
     
  5. donepearce

    donepearce Well-Known Member

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    Try tapping it with something non-metallic it should only make a dull thud.
     
  6. Bad Penguin

    Bad Penguin Well-Known Member

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    Might sound silly, but add a piece of a sponge to the underside of the pickup.
     
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  7. DrBGood

    DrBGood Well-Known Member

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    You tried that and it works ?
     
  8. Bad Penguin

    Bad Penguin Well-Known Member

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    Yes, to a P90 pickup in a Gibson Blueshawk.
     
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  9. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    I have a few questions for you, PTL.

    HOW LOUD do you HAVE YOU AMP set?
    I am guessing, you set the guitar volumes above 7 too.

    THE next question, HOW far from the amp/ and what speakers are you using? I am thinking there is a cause and effect relationship from air movement, sound wave, note causation. Think Feedback.

    Now I am in agreement with Bad Penguin and DonP and using your own statement about the bridge pups doing it as they are set higher and closer to the strings.

    Your logic on the springs seems to make sense but maybe the reverse logic is true. More SPACE under pups can act more like a drum in reflecting sound or air around the back of your pup. My friend Ron has a BEAST of an LP and I asked him how it sounds so good other than his skill. He said his humbuckers are screwed directly to the wood. In other words, he got them adjusted where he likes them, and then had the space measured in behind them and filled with the precise thickness of a wood shim and as you can guess, no moving around. I am equating Bad Penguin's foam suggestion to be a similar effect, reducing the space the pup can move in and cushioning the pup from forces that it can " pickup" unwanted noises from.
     
  10. DrBGood

    DrBGood Well-Known Member

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    Brillant ! I'm due to change strings on my LP Ultra, I'll try that. It might also add that little meat that is missing from my Jr.
     
  11. donepearce

    donepearce Well-Known Member

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    There seems to be some cross-purpose going on here. When a pickup feeds back it isn't normally because it can move a little on its mounting - it's because the internals are loose in the can, normally some of the windings. You need to work out which it is before diving into a fix. Generally loose internals will feed back at a high pitch - a squeal. Loose mounting I can't say - I've never experienced feedback from that cause.
    If it is a squeal from the internals, wax potting is the only fix.
     
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  12. PermissionToLand

    PermissionToLand Well-Known Member

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    Yeah, I guess it's not the typical feedback sound so maybe that was the wrong word to use. It's more of a mid-pitch hum, I guess? And it happens with the strings palm-muted, so it doesn't act like traditional feedback. I think I'm going to find some foam to stuff under the pickup.

    I'd heard Malcolm Young would stuff socks in his pickups cavities to prevent feedback. This also happens to be my LP Ultra which is chambered, much like a Gretsch Firebird.
     
  13. DrBGood

    DrBGood Well-Known Member

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    LOL ... you just made me realize that if I want to put wood blocks under my pickups, I'll have a huge void to fill. Might as well buy a non chambered LP :) But I'll try it with the Jr.

    I get that low feedback with the Ultra if I'm too close to the amp at high volume. I just move away. Mind you I'm not playig a 100W full stack.
     
    Last edited: Jan 26, 2021
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  14. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    Good catch on that, DonP. Sometimes when folks are trying to get help and describing a symptom, their mind hears or senses it, but conveying exactly what the issue is turns out to be harder to not be vague on the details for those he asks for help.

    Not sure if what is being described as feedback/vibrating etc might not be something another member and others elsewhere on the web have described as Wolftones.

    Just bringing that up if PTL might not be hearing that.
    https://www.seymourduncan.com/blog/the-players-room/eliminating-wolf-tones
     
  15. PermissionToLand

    PermissionToLand Well-Known Member

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    Af I recall correctly, the Ultra has a sort-of center block under the pickups. Or at least one of them. It's not fully hollow, anyway. I guess I'll find out soon.

    We've been jamming in a small living room and our drummer doesn't know how to play lightly, so even with my little 65w combo, it gets very loud.
     
  16. DrBGood

    DrBGood Well-Known Member

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    This is the inside of your Ultra.

    Chambered.jpg
     
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  17. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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  18. DrBGood

    DrBGood Well-Known Member

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    It's OK. I glued it back together, it doesn't show ... much :rofl:

    As you see on the image of the chambers above, both pickups are screwed to the top cap, so kind of suspended.


    Neck pickup chambered.jpg
     
  19. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    WOW JEAN< I had no IDEA one could see inside the weight reliefs on these guitars like that. Thanks for posting that pic.

    I did know pups are suspended and usually have always been with only the pup rings screwed down. My only LP's have been non weight relieved versions.

    What is that pickup model on your guitar?
     
  20. DrBGood

    DrBGood Well-Known Member

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    That's the pickup that comes in it, '57 Alnico Classic. Not bad pups, but they have since been replaced by a set of boutique Tyson Tone PAFs I won and I had nowhere else to put them.
    I meant to say, suspended over a vast resonance box.
     

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