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Coil Tap Question

Discussion in 'Pickups & Electronics [BG]' started by Hevy T, Jun 4, 2012.


  1. Hevy T

    Hevy T Supporting Member

    Jan 11, 2011
    Lethbridge, AB Canada
    I was asking my tech about my G and L L2000 Tribute.

    I told him that I wanted to ad a coil tap to the bass. He told me that that was what the series parallel switch did.

    Considering I had a bass back in the 80's that I had wired so I could isolate any coil at any time, I think he is wrong.

    Can I wire the guitar so that I have the series parallel and also be able to go from humbucker to single coil with a switch for each pup? I think I should be able to!!
     
  2. Coil tapping can be done only with coils that are wound with taps. You're referring to a coil split.

    Sounds like you want series/single coil/parallel switching? That is indeed done the same as a series/parallel switch, but with a DPDT On/On/On switch; also known as a SP3T.
     
  3. Hevy T

    Hevy T Supporting Member

    Jan 11, 2011
    Lethbridge, AB Canada
    Thanks, so I guess we are both 1/2 right eh?
     
  4. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    The series/parallel switch on the G&L does work to split the pickups to single coil. It uses a cap to do this so they are single coil in the high frequencies and humbuckers in the low frequencies. This makes them quieter and a little fatter in the low end.
     
  5. scotch

    scotch It's not rocket science!

    Nov 12, 2006
    Albany, NY USA
    Please see Profile for Endorsement disclosures
    Curious: how does that work? Do the G&L pickups already have a 4 conductor output that the switch also splits?
     
  6. Smilodon

    Smilodon Supporting Member

    Feb 18, 2012
    Norway
    That one sounds pretty interesting. :)

    I assume they wire it to be parallel but one of the coils have a cap in series, correct?

    Do you know what value caps they use? I want to test this out. ;)
     
  7. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    All you have to do is take a series wired humbucker, and where the two coils connect together, connect a cap, and wire it to ground. Now one of the coils is shunted to ground, but since caps block low frequencies, the coil is cut in the high end, and not the low end.

    I first saw Bill Lawrence do this trick.

    G&L uses a .1µF cap, but you can use a smaller value as well. I've used .02µF and .047µF. You will get different tones with different value caps.

    Some people think the cap is there as a bass boost (the OMG switch), but it's just because it's retaining both coils in the low end.
     
  8. scotch

    scotch It's not rocket science!

    Nov 12, 2006
    Albany, NY USA
    Please see Profile for Endorsement disclosures
    Gotcha!
     
  9. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    David -

    Can one SPDT or DPDT switch be used to do G&L/BL trick (or a regular split) to multiple pickups or is it necessary to use a 4 pole switch? I am wondering if having all multiple series joints connected together would screw up humbucking mode (some kind of interaction).

    It seems like multiple switches or a 4 pole switch would be needed, but I have seen wiring diagrams on the Seymour Duncan website that tap three humbuckers with one push/pull pot. That seems to suggest otherwise.

    I am thinking of modifying my M2500 with a third pickup and a switch to split all three pickups (via capacitor trick). Since its an active bass with no PG I want to keep the extra wiring to a minimum.

    The third MFD pickup would be toward the neck and spaced the same as the other two.

    Thanks - your technical insights are always helpful and much appreciated!
     
  10. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    If you want to switch the humbuckers to single coil, you only need a DPDT switch. Each half would work for one pickup.

    To illustrate this, here's the Stew Mac page on pickup wiring for DiMarzio pickups (they have a bunch for all the different color codes:

    http://www.stewmac.com/freeinfo/Electronics/Color_codes/i-dimarzio.html

    So here's the humbucker to single coil wiring:

    dimarzio-2.gif

    So that will connect the series connection to ground, which will turn off the North polarity coil (red/black). If you wanted the other pickup to turn off the south polarity coil, you would connected the terminal on the switch to hot instead of ground. So you can do each side differently.

    Then switching the switch will give the two outside, or inside single coils, which will hum cancel.

    If you want to do the trick with the caps, usually you do that between the series connection and ground. You can also do it between the series connection and hot, but it gives a different kind of effect. it kind of tunes the resonance on the pickup.
     
  11. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    I figured I could use the two halves of a DPDT for two pickups, but if I go to three pickups I would have to use a 4 pole switch I guess? If the series connections are joined to one another that would mess up humbucking mode, right? Kinda confused about that part. Duncan wiring diagrams show all three series connections going to the same switch terminal for routing to ground (to cut one coil on each).
     
  12. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Yes, you need a pole per pickup. 3 poles will work, if you can find one. If you join the series connections together, you wont be able to switch a pickup off. You will always have them connected together, and they wont really hum cancel.

    Where does Duncan show that?

    Personally I would use a separate switch per pickup, and I tend to do series/parallel over Series/Single coil. It sounds similar and doesn't hum. But then you need a DPDT switch. If you use an on-on-on switch, you can do series/single/parallel.
     
  13. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    Normally I would agree on doing three switches with series-parallel-single on each. I was trying to keep the switches to a minimum (for a change) and figured the capacitor trick would give me a good compromise.

    A 4 (or 3) pole switch makes more sense to me. Here is the duncan diagram. I may be misinterpreting...always thought it was too good to be true....

    http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=1lil1v1t5w3s
     
  14. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
  15. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    Makes sense; thanks David!
     
  16. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    Thanks again. This is the application I was thinking of, but I'm sure I'll fiind other uses for the 4 pole switch.

    M2500Tribute_zps4dea4d24.jpg
     
  17. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    David, what effect does the capacitor value have in this application? Higher value (eg: 0.1) = more bass and less hum, or is it the other way around where lower value (eg: 0.047) = more bass and less hum?

    I ordered a 4 pole switch today. Might use different values for each pickup.

    Thanks Professor Schwab!
     
  18. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    OK, what's going on is the cap splits the pickup (not tap, split) only at the high frequencies. So the low end is still hum canceling.

    Larger values move the cross over point lower.

    This is assuming the cap is between the series connection and ground.

    That's my brother! (seriously)
     
  19. Doner Designs

    Doner Designs Steve Doner Gold Supporting Member

    Jun 2, 2012
    Metro Chicago Area
    Doner Designs is an alias for Steve Doner
    I'm pretty sure I understand the concept (thanks to you sir). Also have used caps for a passive bass cut control. For bass cut controls I used a value about 1/10 the size of typical treble cut capacitors - like 0.0047 vs 0.047- and in series instead of parallel.

    Anyhoo, it sounds like G&L uses 0.1mf in this coil splitting application and if I used 0.047 (smaller value) instead, the crossover frequency would be higher. So in that case, some of the mids would be hum cancelling too and there would probably be less hum overall...since more of the spectrum is in hum cancel mode. Right?

    If I'm understanding correctly, maybe it would make sense to use something like 0.033 for the bridge, 0.068 for middle and 0.1 for far neck?
     
  20. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Try different caps and see what you like. I used to use a switch to switch between caps on a guitar.
     

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