OMG Mode for Jazz Bass

Discussion in 'Pickups & Electronics [BG]' started by Brent's Groove, Jun 15, 2020.

  1. Brent's Groove

    Brent's Groove

    Mar 14, 2007
    View attachment 3868876

    I have a jazz that I have modded with a series/parallel switch on the volume pot. I would like to install a resistor to turn series mode into OMG mode, as seen on some G&L basses.

    Unfortunately, I'm no electronics whiz but I can follow a diagram.

    I have two questions: 1) what value resistor do I need, and 2) where do I install it within the attached diagram to shunt the high end from the neck pickup when in OMG mode.
  2. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    It's not a resistor, it's capacitors:

    The top left of the schematic is where you want to look.

    G&L Wiring Diagrams and Schematics

    Here's the associated wiring diagram:
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  3. fermata

    fermata Guest

    Nov 10, 2015
    You should use a .1 uF capacitor for OMG mode.

    I can't see your attached diagram, @Brent's Groove, but assuming it's like this, you just need to replace the jumper with the capacitor. One caveat: the OMG circuit means your pickups won't be humbucking any more, so you'll hear some 60 Hz hum.

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  4. Brent's Groove

    Brent's Groove

    Mar 14, 2007
    That is very helpful. Yes, that diagram shows me where I need to put the cap.

    And I'm going to try this mod with a new set of Seymour Duncan Apollos, so I'll be able to experience it hum free
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  5. sikamikanico


    Mar 17, 2004
    Cool, report back on how it works, I’ve been curious about this on a J bass!

    if you don’t like it, another simple trick is to wire a cap in series with the bridge pickup to kill some of its low end... it’s supposed to sound fuller when blended with a neck pickup (less mid scoop).

    I may just need to get a J bass and experiment :)
  6. Use this diagram for Series/Bridge coil/Neck Coil with OMG mode if you so desire:

    Just don’t mind the bottom switch. I used this with MM pickups successfully.

    the other diagram posted by @fermata I never actually tested. I just traced out the wiring and drew that up...assuming....
    So test it if that works before you hang me.
  7. fermata

    fermata Guest

    Nov 10, 2015
    Yes, a la Rickenbacker. A .01 uF capacitor works well for this. But because it flips the polarity of the pickup, the two J pickups would no longer be humbucking, so it may be better with a PJ setup. The other side effect is that the bridge pickup will no longer work very well soloed, if that's a concern.

    Also, it only works when the pickups are wired in parallel with each other, so it's not ideal for the OP's wiring, since it would cut bass on both pickups wired in series. Speaking of series wiring...

    If one ends up preferring series to parallel or one doesn't like the volume change between series and parallel and is OK getting rid of the parallel mode option, @eastcoasteddie's diagram above is very clever.

    I've used to good effect on two basses (using a .1 uF cap). Switch up is standard series wiring, and the other two positions (using an on-on-on switch) are two--count them, two!--OMG modes.

    With a MM pickup, where the coils are very close together, the difference between the OMG modes is a shift in midrange emphasis. A series-wired Jazz bass has a humbucker with very widely-spaced coils, so I would anticipate a significant difference between neck pickup OMG and bridge pickup OMG, and they'll probably both sound cool.
    Last edited: Jun 17, 2020
    sikamikanico likes this.
  8. And that’s exactly why I did this, because I simply cannot stand the volume drop between Parallel/SC and Series. A nice way to combat that is to add a Mini trim pot to the Series setting in order to dial it back to match output of the other modes. I have yet to try it, though.
    So when I wire up MM pickups, I usually prefer Bridge Coil/Parallel/Neck Coil as I did with my latest project. But if I go with Series wiring, I would use OMG on both SC modes for balanced output.
    The Jazz pickup spacing with OMG modes would definitely sound interesting, I am intrigued.
    Also, I came up with that wiring purely by accident. I was wiring the bass up as per the first diagram (the one I never tested) and accidentally wired it up as the one I posted. I was shocked at what I did and never corrected it to the first diagram...which is why I never did test it...