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Wiring Jazz bridge pickup as dummy coil

Discussion in 'Pickups & Electronics [BG]' started by Rockin Mike, Oct 29, 2015.


  1. Rockin Mike

    Rockin Mike

    May 27, 2011
    I have a bass with two identical jazz-style pickups, neck and bridge.
    Is it possible to rewire the bridge pickup as a dummy coil to the neck pickup and run the bass as a single-coil hum-cancelling setup?
    Maybe by removing the magnets from the bridge pickup and wiring it in reverse, or somesuch?
     
  2. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    Most jazz bass pickups are made so that you can't remove magnets without destroying the pickup.
     
  3. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Supporting Member

    I cannot help you on the subject, I am just commenting so I remember to come back to this thread. I am very intrigued with your idea.
     
  4. Rockin Mike

    Rockin Mike

    May 27, 2011
    I'm not sure removing the magnets would be necessary. It might be all in the wiring.
     
  5. Not sure how well this would work, but you could try putting the bridge pickup as low into the body as possible, and then raising the neck pickup as high as possible; it may not be perfect, but you should be able to accomplish something to that effect.
     
  6. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    The magnets need to be removed so the pickup doesn't sense any string vibrations. If it did, it would "cancel" some of the strings' sound too. If you can't remove the magnets, mount the pickup as far away from the strings as practical.

    A passive dummy-coil setup is possible and will work, BUT the extra impedance of the dummy coil means it won't sound exactly like a solo'd pickup.
     
  7. Get yourself a $5 ceramic pickup on eBay, and pull the magnets off.
     
    BassikLee and Will_White like this.
  8. Rockin Mike

    Rockin Mike

    May 27, 2011
    I thought the dummy coil had to match the pickup coil as closely as possible, in impedance, number of turns, stuff like that.
     
  9. Not really. What matters is matching the output level as closely as possible. A significantly lower impedance dummy coil would put more loading on the audible coil, so avoid that, but on the other hand, here is something worthwhile to consider; Grab a really high impedance and high output pickup, and dial back the output to a perfect match with your audible coil, using a trim pot. The combination of the high output impedance, and the resistor will equate to a greatly reduced load on the audible coil, while still humcancelling.
     
  10. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    in parallel, yeah; most dummy coil implementations i've seen put the coil in series, so a lower impedance dummy is a good thing, it'll choke the tone slightly less. (it'll still choke the tone, which is why dummy coils aren't more popular).

    take the magnets out and stuff it in the control cavity away from the strings, oriented to be in the same plane as the pickup coil and properly RW/RP from it.
     
  11. Rockin Mike

    Rockin Mike

    May 27, 2011
    I take it "RW/RP" = reverse wired/reverse polarity?

    The goal of doing this is to make a Jazz sound more like a P without having to rout wood; the novel part of the idea is leaving the bridge pup in place. Given that consideration, is it still better to use low impedance wired in series or high impedance in parallel with a trim pot? Is a trim pot beneficial in the low impedance/series scenario?
     
  12. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    huh?

    a dummy coil will do nothing of the sort, and if it's anywhere near the strings it won't be a dummy coil, it'll be another pickup.
     
    line6man likes this.
  13. Yeah, dummy coils are for achieving humcancellation with a single coil pickup. If you want a P bass tone, a better idea is to install a series/parallel switch.
     
  14. Rockin Mike

    Rockin Mike

    May 27, 2011
    To clarify, A soloed neck pickup on a Jazz is closer to the sound I'm looking for. It's not a P pickup, but it's closer than a Jazz with both pickups full-on. Problem with soloing a Jazz neck pickup is hum in some venues. I thought if the bridge pickup could be made into a dummy coil it would allow for a hum-canceling soloed J neck pickup, which might be easier and cheaper than routing and replacing the electronics with an actual P pup.

    Since the bridge pickup is made with epoxy, there's no getting the magnets out.
    I'll try lowering it as much as possible and see what that does.
    Next step would be buying an actual split-coil J neck pickup and leaving the bridge pickup unwired.

    Thanks for your help and advice you have helped me understand some of the issues around what I had in mind.
     
  15. Rockin Mike

    Rockin Mike

    May 27, 2011
    What will that do?
     
  16. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    gotcha;

    it'll only be a dummy coil if it's removed entirely from the string path. i suppose removing any foam or springs from under it and dropping it all the way down will reduce its signal input, but either way, like any dummy coil it's gonna be a huge tone suck on the neck pickup.
     
  17. Rockin Mike

    Rockin Mike

    May 27, 2011

    Well I took the foam out and dropped the bridge pup as far as possible. From what I understand that doesn't make it a dummy coil, and my ears tell me it just turned the bridge pup volume into a "tone suck" knob.

    Maybe I'll just learn to use a router and put a P pickup in the neck position and leave the bridge unwired.

    Thanks everybody for your help and advice.
     
  18. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    I'm voting for a split coil jazz shaped pickup in the neck, and disconnecting the bridge pickup entirely. That will keep you from having to route the bass, the mod will be easily reversible, and as a bonus, there are tons of split coils in jazz pickup shape for you to consider.
     
  19. Although not quite exactly the same tone as single coils, humcancelling Jazz pickups are available.
     
  20. Silky beat me to it.
     

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