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  • #1

    Humbucker Hum?

    Hello all,

    I recently swapped out pups and pots in a LP. Stock it had the 490/498 combo with 300k pots.

    I moved the 490 neck to the bridge and put a Duncan Seth Lover "PAF" I had lying around in the neck.
    On both I put new pickup covers (nickel). I also swapped out the stock 300k pots for 500k's.
    I used the existing wiring and only re-soldered it to the new pots.

    The guitar was pretty dead quiet before I did the swap. Now I have a 60 cycle hum similar to my Strat (with Texas specials) not quite as bad. It goes away when I touch the strings.

    When I turn down the volume/tone controls to approx what would be 300k and below the hum goes away (to a degree). My question is, is this normal to see a jump up in hum with 500k pots in a humbucker circuit?
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  • #2
    "My question is, is this normal to see a jump up in hum with 500k pots in a humbucker circuit?"

    No.

    The reduced hum with the volume rolled off is also a result of the series resistance of the pot (be it 300k or 500k). The signal, and the noise, will find the path of least resistance. The 200k "load" difference will make almost no noticable difference in hum.

    "It goes away when I touch the strings"

    Thats normal. YOU are the guitars ground. The noise you're hearing is grounding to YOU when you touch the strings.

    Do you have the same trouble with both the neck and bridge pickup, or just the new neck pickup??? On the stock Gibson pickups (with the cover shield) the shield is grounded to the - side of the pickup, which is typically grounded, and so, the shield is grounded.

    Did you ground your new pickup shields???

    HTH

    Chuck
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #3
      Hello Chuck,

      I get hum in each position a little less in the middle position.

      The shielded cable (cable shield) coming out of the Gibson is soldered to the pup base plate. On the Duncan Seth Lover this is not. Should it be? They don't come stock like this...

      Also I was told to put a small piece of masking tape over the slugs before putting on and soldering the new covers to base to help out with microphonics. I'm not sure if that would have anything to do with it, would it?

      TIA

      Comment

      • #4
        "I get hum in each position a little less in the middle position"

        You should have the same level of hum in the bridge pos. as you had in the neck pos. before...Provided you wired the pickup and it's grounds the same. So it may be that you simply didn't notice the hum before. Or that it grounded out when you touched the strings.

        "On the Duncan Seth Lover this is not. Should it be? They don't come stock like this"

        I don't remember if the Duncans have the shield soldered to the base. They use that funky foil shield with the bare wire lead. And there is no solder on the bottom of the plate, so it's hard to tell. If you can find the "other" end of the shield wire go ahead and solder it to the base. But do it on one of the legs and not the plate area. You could f@#k up your pickup otherwise. Even then you still have to insure contact between the base and the cover. You can do it by soldering a small wire from one of the base plate legs to the inside bottom of the cover. I've even used copper foil for this.

        "Also I was told to put a small piece of masking tape over the slugs before putting on and soldering the new covers to base to help out with microphonics. I'm not sure if that would have anything to do with it, would it?"

        Sure it could. At least it did for whomever suggested it. I think a small piece of some kind of foam rubber right on top (under the cover) would do the same thing. I once had a guitar that I had a bitch of a time troubleshooting the feedback on. Turned out to be the pickup adjustment springs. I replaced them with some carefully sized snips of surgical tubing and the feedback was gone...So, you never know.

        FWIW I think it could be that your just noticing the hum for the the first time because your critical of your work. But if the hum is indeed louder than before, even with the pickup that guitar was already using, then I'm stumped. If it was a grounding issue then touching the strings would not silence the hum...

        HTH

        Chuck
        "Take two placebos, works twice as well." Enzo

        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

        "If you're not interested in opinions and the experience of others, why even start a thread?
        You can't just expect consent." Helmholtz

        Comment

        • #5
          Chuck, I did the full setup on that guitar last night. The pups were really low compared to Gibson specs. I did not realize this at first. I've not owned a LP since my second guitar many moons ago. I adjusted them to factory heights and the hum problem has been significantly improved.
          Maybe a tad noisy (not much) compared to the old pups, but I do have that Seth Lover PAF in the neck...
          Overall I'm really happy with the new setup. That 490 makes a really sweet bridge pup with a Duncan Lover in the neck.
          Thank you for all your help. I really appreciate it.

          Comment

          • #6
            try switching the leads on 1 pickup, the ground to hot and hot to ground. should do it..

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