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New Pickup Hum

Discussion in 'Hardware, Setup & Repair [BG]' started by td1368, Mar 26, 2001.

  1. td1368


    Jan 9, 2001
    I recently installed a new set of Dimarzio Ultra Jazz Pickups. I followed the installation instructions
    thoroughly. The only problem is a slight hum. I don't know if I am properly grounded. When I removed
    the old pickups I removed the copper wire strip to the bridge and the plates beneath the old pickups
    and the grounding wires.

    I have a grounding wire from my first pot to a plate in the control cavity, That's it. When I add treble either
    on the tone knob to on my amp the hum gets worse. Also when my hands on the strings the hum stops.
    I know the new pickups are humbucking so I assumed the old grounding was not necessary.

    Any Ideas?
  2. you didn't say if you put them back or not. if you didn't, try rewiring those back into place, and i'll bet your hum will go away. they were there for a reason.
  3. td1368


    Jan 9, 2001
    I called technical assistance at Dimarzio and the tech said the hum could come from the pickups having a higher impedence and output level.. Also he said the grounding plates could interfere with the sound of the pickups. I think I'll try putting the plates in anyway. He also suggested copper wire sheilding in the control cavity. Like I said the problem is only when my hands are not on the strings so I quess I should shut up and play.

    I thought humbuckers where supposed to be totally quiet. Anyone have these pickups installed with similar experience?
  4. rickbass

    rickbass Supporting Member

    I haven't owned the Ultras, but I do know they're advertised as "humcancelling," not, "humbucking." There may be more than just a semantical difference. If replacing all the good copper you took out doesn't do it, then making sure your control cavity on the MIJ is TOTALLY shielded with copper, (haven't owned one of those either).

    The "hands on the strings" thing is a classic giveaway for electrostatic noise. TOTAL pickup and cavity shielding is the classic cure. But you talk about removing some things and even if your cavity is well shielded, you still can get hum if it is not connected to ground. Apparently, your strings and tone pots are acting as a big hum attena. Shielding and grounding are the usual cures.
  5. the grounding wire to the bridge is very important for reducing hum when your hands aren't on the strings. the control cavity shielding is nice, but not 100% necessary unless you have active electronics.
  6. td1368


    Jan 9, 2001
    I reinstalled the bridge grounding wire and it did reduce the hum. Still I think I'll try the sheilding also.

    FYI I found a site regarding sheilding and grounding for mostly elec guitars, specifically stratocasters. However the dude does talks about grounding and sheilding in combination to reduce hum in pickups. There is alot of info on wiring if anyone is interested


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