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JBass Dummy coils?

Discussion in 'Pickups & Electronics [BG]' started by FritzM, Jan 7, 2005.


  1. FritzM

    FritzM Supporting Member

    Jun 21, 2001
    Madison, MS
    This may be a dumb question, but here goes.

    1. I have a master built Fender Custom Shop Jazz with unbelievable sounding pickups. I only use the back pickup. I just like that sound.

    2. I haven't been happy with the hum canceling pups that I have tried because they don't have the richness and punch of my single coils.

    3. Is it somehow possible to deactivate the neck pickup from making sound, but turn it on to create a dual coil scenario? Kind of like making the neck pickup a "dummy" coil.

    4. Sorry if this is stupid, but the 60 cycle hum is driving me crazy on certain gigs.

    Thanks___Fritz
     
  2. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    No, you can't use the neck pickup to cancel noise without it also having an impact on the sound. If you want to eliminate the noise, try shielding both your control cavity and your pickup cavities. You would be amazed at the difference that shielding makes.
     
  3. phatcactus

    phatcactus

    Apr 2, 2004
    Chicago, IL
    I bet some pickup maker could build you a magnetless J neck pickup. I'm not sure what it'd do to the sound, but it might be worth a look.
     
  4. DubDubs

    DubDubs

    Aug 23, 2004
    Los Angeles
    do what xyllion said. There was a very recent thread about how to do it check that out.
     
  5. Bassic83

    Bassic83

    Jul 26, 2004
    Texas, USSA
    Out of curiosity, what humbucking Js have you tried? I love my DiMarzio UJ's. I also shield like a mo' fo'... ;)
     
  6. Tritone

    Tritone Supporting Member

    Jan 24, 2002
    Santee, America
    What do you think about adding a 3rd dummy coil ala Alembic?
     
  7. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Sheilding is the best if you don't want to alter the sound. If you don't mind changing pickups, you could try some vintage DiMarzio's. I think what they do is a side by side coil design, so that two strings are over one coil, and the other two strings are under the other coil. This tend to have a good single coil soind without hum.
     
  8. _Unregistered_

    _Unregistered_

    Nov 3, 2004
    The two pickups used together only cancel hum because they are wired opposite. As a result, the hum induced by EMI, RFI and "line hum" (60 Hz a/c) causes opposite signals to appear in each pickup, that when summed cancel.

    The "sound" of the string doesn't exactly cancel, because the pickups are in different places along the string, and thus each sense a different harmonic "image" of the string. I'm sure you have noticed, however, that SOMETHING does in fact get cancelled in the sound when both coils are on...and that's probably what you're not liking. What gets cancelled is the harmonics that are actually sensed by both of the coils.

    If you were to energize the second (or a third) coil, but not sum its signal, hum cancellation would not occur.
     
  9. Matteran

    Matteran Banned

    Jan 1, 2005
    Santa Rosa, CA
    just out of curiosity, when you guys say shield everything, that's just putting the copper sheeting stuff everywhere, right? Like around the pickup routes, and everything?
     
  10. phatcactus

    phatcactus

    Apr 2, 2004
    Chicago, IL
    But if the neck "pickup" was just a coil and had no magnets in it, it wouldn't sense any string vibration. Wouldn't it cancel hum without affecting the bridge pickup's signal? That's how I always thought dummy coils worked.
     
  11. bluesgeek

    bluesgeek

    Jun 27, 2004
    I have a dummy coil in my strat and it looks like a pretty much regular pickup without any polepieces. Might be worth getting hold of a cheap pup and trying it?

    Incidently, the dummy coil on my strat works great :) its wired in parallel with all the pups which are custom shop 54's (so they are all wound the same way) so cancels noise in all positions :hyper:
     
  12. _Unregistered_

    _Unregistered_

    Nov 3, 2004
    Energizing a coil that was wired in reverse AND summing its signal as long as it wasn't sensing the strings would cancel the hum without changing the tone.

    What I'm not sure of is whether a coil without magnets would completely fail to sense the strings. It may still sense the strings somewhat, although probably considerably less. However, I can't claim to know that much about magnetic theory.

    Anyone here with more knowledge of applied magnetic fields? Can you confirm that a coil without magnets senses NO string signal? ...or would you ideally need to locate such a "dummy" coil away from the strings?
     
  13. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    I'd suggest solving your hum problem "first". After that's fixed, you can do whatever you want with your pickups.
     
  14. Bassic83

    Bassic83

    Jul 26, 2004
    Texas, USSA
    Wouldn't the dummy coil "load" the signal, due to it's acting as an air-gap coil, or inductor? A bunch of wire wrapped around a bobbin would be a coil inductor, correct?
     
  15. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    Stew Mac sells shielding foil which is copper tape with a conductive adhesive. This is absolutely the best stuff to use. Be sure to connect the shield to ground when you put it in. If it isn't grounded, then it won't work. You can also use a conductive paint, but the foil is superior.
     
  16. FritzM

    FritzM Supporting Member

    Jun 21, 2001
    Madison, MS
    I think there is a little confusion. I do not have a hum problem due to a grounding or shielding issue. I ONLY use the back pickup, so I'm talking about the 60 cycle hum due to the pickups being out of phase. I don't think shielding can completely eliminate this. My bass is dead quite with both pickups turned all the way up.
    I have tried the Ultra Jazz, and they are really good, but these were specially wound by the Fender Custom shop and they sound unreal. Very hot output and VERY rich. The Norstrand might fit the bill, but at $229.00 a pair, I would rather try something else first.

    Thanks___Fritz
     
  17. "The 60 cycle noise when the pups are out of phase...."

    Huh??? That does not make sense to me, perhaps you could clarify more. (If it's 60 cycle hum it seems like a shielding issue.)
     
  18. FritzM

    FritzM Supporting Member

    Jun 21, 2001
    Madison, MS
    OK,
    I'm not getting pops and crackles normally associated with grounding issues. Its just normal single coil hum. Actually, I can now see where sheilding might help. I was just hoping there was a way to make it dual coil without the neck pickup being heard. It may be easier just to get an UJ bridge pickup for $55.00. But, that would definitely change the tone.

    ___Fritz
     
  19. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    Single coil hum can be reduced or eliminated through proper shielding. Trust me on this one. Single coils do not have to hum just because they are single coils.