Humbucker Pickup Hum Problems

Discussion in 'Guitars in General' started by ripoffriffs, Apr 27, 2005.

  1. ripoffriffs

    ripoffriffs Supporting Member

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    I would like people's input on this situation.

    My stock bridge & neck humbucker Pickups on a Gibson SG '61 Reissue (small pickguard model) has a low frequency hum. It gets louder as you turn up amp gain or volume or when I turn on my Fulltone overdrive pedal.

    I have eliminated ground loop causes between my pedal board (powered by Dunlop Brick) and amplifier. I have eliminated the amp itself as the cause of the hum, Dr Z amps are very quiet.

    Here's how I know it's the guitar's pickups: I merely turn the pickup selector to the middle position and the hum disappears.

    I experience this same problem on another guitar equipped with a Carvin M22SD humbucker. Again, I merely turn the PU selector to an in between position and the hum disappears.

    I do not hear this problem with my 90's PRS EG (US models). I do not hear this problem on the Fender Noiseless stacked humbuckers either.

    If the solution is to merely change pickups, I am ready to do that. But which one? But could there be a solution of merely correcting the wiring inside the guitar?

    Some input would be great.
     
  2. The_Whale

    The_Whale Member

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    I have the same issue with my Heritage 535. As far as I know it has stock pickups, but they are not completely humbucking.

    Let me me explain: When selecting only the neck pickup or only the bridge pickup, a small, yet noticeable amount of noise comes through. When selecting both pickups, the guitar is silent.

    I suspect that one coil of each humbucker is intentionally wound with more wire.

    Does anybody know anything about this?
     
  3. The_Whale

    The_Whale Member

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    Hey Rip, it seems we're the only two people in the world with these "special" pickups.

    They must be very valuable.
     
  4. righthandman

    righthandman Member

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    I've noticed it on my 335 and Les Pauls--neck or bridge humbucker alone produces a little bit of hum which goes away when the pickup selector is in the middle. I've never given it much thought since I never notice on a gig, only when I'm playing at home. Sorry I can't help other than to say I've experienced the same thing. Surely somebody knows why this happens.....
     
  5. The_Whale

    The_Whale Member

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    You've noticed it on all of your 335/LP guitars?

    I haven't noticed this on any other humbucker equipped guitars i've owned played except the Heritage I have now.
     
  6. John Phillips

    John Phillips Member

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    I have noticed this too, but it's never bothered me or made me think really about it before.

    I have two ideas, neither of which may be correct... :)

    #1 - when the pickup selector is in the middle position, both volume and tone pots are connected. This will load down the pickup output and/or the amp input (depending on where the hum is actually coming from) quite a bit more, maybe enough to kill the hum. Not only that, the combined impedance and inductance of both pickups together is half that of either alone, which will do the same thing.

    #2 - although the pickups are humbuckers, they aren't 'perfect', since the coils are most likely not truly balanced and aren't quite in the same physical location, and a little hum will always be present. But in a normal two-humbucker guitar, the magnetic fields of the two pickups face in opposite directions, and this may make them better at rejecting hum when they're on together - it will be a small difference, but it might eliminate that last few percent of hum you're hearing.

    It's fairly easy to test this theory - just rotate (not phase reverse) one pickup and see if it still cancels the hum in the 'both' position. If it does, it's #1, probably.
     
  7. The_Whale

    The_Whale Member

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    Yeah, I suspect that the "Les Paul" style switchgear has something to do with it.

    Maybe the pickups are dead silent, but the "LP style" wiring and controls produce more noise, which (for whatever reason) is attenuated when both pickups are engaged?

    I never really noticed it on other guitars I've had in the past though, that's why I assumed it is the pickups. It still could be the pickups.
     
  8. righthandman

    righthandman Member

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    Whale--yeah, I've noticed it on my 335 and two Les Pauls. The hum goes away with the switch in the middle position until you roll back one of the volume knobs, then it hums a little. I've really never given it much thought but I notice it.
     
  9. The_Whale

    The_Whale Member

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    The fact that others have the same problem makes me feel better.

    The noise isn't that bad, it's that it is worse than (say) a strat set to 'in-beteen'. It's bad enough to notice and sometimes be annoying, yet isn't bad enough to motivate me to do anything about after living with it for a while.

    I haven't played this guitar in over a year (!), I'm certain the next time I play this guitar I'll notice it again and ask this question again (perhaps on this very forum).
     
  10. gameover98

    gameover98 Member

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    resurrecting this old thread 'cause i'm having the exact same problem and haven't been able to find anything on it. maybe someone has some more information now?

    i just got my LP Std DC some new WCR pickups. they are great!! but now my guitar hums, which isn't horrible, but i'm wondering if it's something not wired right that i should get fixed, or if i should just learn to live with it...
     
  11. Strat58

    Strat58 Member

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    Hi try it first without any pedals between the guitar and amp, I think you have a groundloop somewhere. If it hums without the pedals then its the guitar(maby the ground has come lose from the tailpiece, or maby the cable is not 100%). If you don't have hum without teh board it must be a groundloop.
    Peace Strat58
     
  12. stratrat2000

    stratrat2000 Member

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    Many modern humbuckers have two coils which are wound unevenly, either with different gauge wire (but to the same DC resistance) or with a different number of turns of wire on each. The reason for doing this is it has been found that humbuckers with uneven coils have more of the "vibe" and "mojo" that guitarists are looking for (as one coil is dominant and the pickup leans slightly towards being more single-coil like). The downside to this is that (as you have discovered) the hum cancelling capabilities are affected.

    The reason the hum quietens with the selector in the middle is that it is usually the opposing coils (slug or screw) on each pickup which are wound hotter - and they are RWRP to each other (basic humbucking theory), so each humbucker produces the interference out of phase with the other, and it then cancels out when the two pickups are combined (almost like a humbucker formed between two full 'buckers - quite cool!).

    Similarly, when you turn one pickup down in an LP-style control arrangement, you are throwing the pickups out of balance with each other - so the hum is not properly cancelled.

    So if the hum is really an issue for you, you can ask for humbuckers with matched coils, but be warned - they do lose a little vibe.
     
  13. go7

    go7 Member

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    Had the same problem with an EBMM Axis Super sport.After wacking my over it and solving nothing I took it to a great Luthier that is very good with wiring problems. Short version $45 bucks later problem solved. He said it was a grounding problem. Good Luck!
     
  14. wgs1230

    wgs1230 Fully Intonatable Silver Supporting Member

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    Sure, it's a grounding problem. The question is, what to do about it?

    1. Check the wiring in cavity, make sure you don't have any cold solder joints on the ground connections to the pots or at a ground point off the output jack.

    2. Check the physical stability of the output jack- once that connection begins to loosen, the wiring can become stressed.

    3. Some vintage-repro pieces come with "correct" unshielded wiring which, in proximity to treble-bypass caps in the control cavity can increase hum. Move them over, tape them off (heat-shrink tubing or electrical tape), replace them with covered wire if needs be.

    4. Consider shielding the entire cavity with copper foil or conductive paint.

    HTH.
     
  15. Wildwind

    Wildwind Supporting Member

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    I didn't read all of this, so forgive me if I'm repeating someone else's post...

    I've had this problem with several Duncans - JBs and Screamin' Demons (Strat and full size versions). I was told these are not shielded worth a darn, hence the problem. If there's a fix for that, I don't know of one. I just swapped them out, problem disappeared. My guitar is immaculately shielded and properly wired - it was completely the fault of the pickups.

    Swapping for Lawrences and DiMarzios fixed the problems. Also, my new Tonerider PAFs don't hum at all. The Duncans hummed nearly as bad as a single coil.

    Maybe this is the deal with yours?
     

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