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G&L "Bass Boost" Circuit

Discussion in 'Pickups & Electronics [BG]' started by bowthing, Nov 12, 2010.


  1. bowthing

    bowthing

    Feb 16, 2007
    Utah
    I was trying to figure out why G&L uses a large (.1uf) cap on one coil of a humbucker in series mode, and started playing around with it on my bass that has dual-jazz pups. It is REALLY COOL! I never used the series setting because the sound was so muddy. By putting a cap across one coil, a ton of the midrange is scooped out, the treble is about as loud as the parallel mode, but the bass is full-on series loud. It sounds, well, like you just cranked up the bass. With the bridge pup soloed I have a totally new sound that I think will be useful. It sounds well-balanced and full, but still "punchy". I think the neck pup will have so much bass that it will be boomy, but I really like the new bridge-only sound.

    You G&L people are thinking "yeah, dude, whatever, glad you finally found out", but I am kind of psyched about these old analog tricks, and getting a new sound from a bass I was a little tired of. To the rest of you with dual coil pups, throw a cap on there and see what you think!
     
  2. Cool!

    I haven't tried it on my jazz, well, cause I like it's sound as it is and I have a couple G&Ls (one with the cap mod) and a P and...

    It is a very cool trick, though. Unfortunately, the coils won't cancel hum, but it's no worse than using one single-coil pickup, so it's usually not a big deal. I would suggest that you wire the cap into the switch so that in series mode the cap is in circuit and in regular parallel mode it is out of circuit. Or, put the cap on it's own switch to use for a totally different tone independent of series/parallel switching.

    Sky's the limit! Have fun, though.
     
  3. bowthing

    bowthing

    Feb 16, 2007
    Utah
    I did wire it so its only connected in the series mode. The pups in this bass were already a little noisy (pretty quiet in parallel but noisy in series), so the loss of hum-cancellation isn't any worse than it was...
     
  4. *ToNeS*

    *ToNeS*

    Jan 12, 2001
    Sydney AU
    I would love to know what you boys are talking about here - what's this cap thing? I have a G&L Tribute and would love to mess around with its guts.
     
  5. petzhopoy

    petzhopoy

    Nov 12, 2010
    Hong Kong
    I am not following,sorry. Any visual aid?big thanks
     
  6. bowthing

    bowthing

    Feb 16, 2007
    Utah
    I'm not sure, but I think the Tribute is already wired this way. A quick explanation:

    A humbucking pickup has two coils side by side, normally hooked up in parallel:

    (+)
    |
    |-----|
    > <
    < >
    > <
    < >
    |-----|
    |
    (-)


    They can also be hooked up in series:

    (+)
    |
    >
    <
    >
    <
    |
    |
    >
    <
    >
    <
    |
    (-)

    And still be humbucking. In parallel, the output is lower (close to what it would be for only one coil) and the sound is pretty balanced. In series, the output is much higher (the voltages generated by each coil are added together instead of averaged), but the resistance through the coils is doubled, so the high frequencies are subdued. The G&L circuit uses a capacitor across one coil (ONE coil only is important!) in the series connection:

    (+)
    |
    >
    <
    >
    <
    |
    |------|
    > |
    < |
    > ==
    < |
    > |
    |------|
    (-)

    What the capacitor does is filter out all but the lower frequencies from the coil it is connected across, and in effect lets the other coil act as a single-coil pickup, adding only bass frequencies to its signal. So you get a much louder bass, but the same mid-high volume.

    The capacitor used is 0.100uf (a #104), though I used a smaller one (0.068uf, or #683) that also sounded good.
     
  7. bowthing

    bowthing

    Feb 16, 2007
    Utah
    Sorry, the spaces don't work out too well for the diagram...
     
  8. Col E Loc

    Col E Loc Supporting Member

    Nov 8, 2009
    Brooklyn, NYC
    Correct me if i'm wrong, but is this a dumb way of saying this:
    The Bridge PU, though filled with Harmonic Content, can seem "thin to a bassists discerning ear.

    the Neck PU can sound "muddy/fuzzy/fury" depending on which language you speak.

    By Adding, Not averaging 1BridgePU Signal + 2Neck PU Low Frequencies we get 3: a new tone, which has the Punch, Clarity & Harmonic Content of the BridgePU With the Neck PU's "WHUUMMPH"

    Yes?

    they sure don't.
     
  9. bowthing

    bowthing

    Feb 16, 2007
    Utah
    Yup, you just wrote the perfect ad copy for Capco, my new series humbucker capacitor company! ;)

    I didn't connect the neck and bridge pickup in series though (like you would do on a jazz). My pickups each have two jazz coils, so its the two coils in one pickup that are hooked in series. (A jazz would be the same thing, just with the coils farher apart---and the choice of which coil to shunt with the cap would make a big difference in the sound I imagine.
     
  10. I got you... I misunderstood. I thought you had a Jazz bass with it's 2 single-coil pickups wired in series mode.

    On my G&L, I have caps on the INNER coils when each is in series mode. Basically the same thing you're doing, only mine are G&L MFDs.

    It's fun to play with.
     
  11. bowthing

    bowthing

    Feb 16, 2007
    Utah
    I haven't had a chance to play a G&L. It seems like this mode with the bass cut control might be even more useful, to dial out a little bit of the boost? Tried it this morning with my amp turned up. Ouch.
     
  12. bowthing

    bowthing

    Feb 16, 2007
    Utah
    My pickups are wound as fronts/backs instead of inners/outers. I think I shunted the neck-side coils, but the bridge-side coils might be a better choice (slightly less bass).
     
  13. delta7fred

    delta7fred

    Jul 3, 2007
    England
    Tributes don't have these capacitors, know as OMG (Oh My God) because of the apparent bass boost they provide in Series mode. It is older USA built G&Ls that had them. Some people love them, some don't. I have never tried it as I have a Tribute, but I can get all the bass I need, and more, using the standard settings.

    The capacitor is put in parallel with one of the coils. This has the effect of shunting the higher frequencies while leaving the bass relatively untouched. The upshot of this is that the bass is almost double the amplitude where the treble is only the same as it would be in parallel mode.

    For wiring diagrams have a look on bassesbyleo.com
     
  14. bowthing

    bowthing

    Feb 16, 2007
    Utah
    OMG is right. Darryl Jenifer needs one of these... Its a punk/dub switch!
     
  15. eastcoasteddie

    eastcoasteddie

    Mar 24, 2006
    NoVA
    Here, check this written up by member DavePlaysBass:

    http://webcache.googleusercontent.c...oc+G&L+capacitor+mod&cd=1&hl=en&ct=clnk&gl=us

    Click on the link at the very top of the page to view it in MS Word. Has diagrams!!!

    This is, in my opinion, a better way of obtaining a "single coil" tone when splitting humbuckers. If you take a standard HB pickup, like a MM-style with 4 leads (Carvin, SD, and just about every other aftermarket MM-style pup out there) in order to split the coils, you take the series wired coils and send one side to ground, in turn canceling out one coil. This in-turn lowers output, too because you lose half the pickup.
    Instead, stick that .1uf cap on the end of those wires that you want to send to ground and you essentially keep all the output and the bass, but get that single coil tone.

    I did that mod to my Dean Sledgehammer with single MM style pickup. I originally did a Series/Parallel/Split coil switch, but parallel and split coils have about half the output as Series. I really love the Split coil tone and this is a much better way to achieve that.

    actually, I modified the usual Series/Parallel/Split Coil wiring by doing this:

    capmod.

    it's a modified diagram by Line6man that he drew up for me a while ago. originally like this:

    standard.

    my modification actually gives me standard series, cap'ed split coil and something else that I haven't figured out yet, but it still utilizes the cap, but sounds a bit clearer than the split coil. It's a parallel circuit, but the cap is now still in the circuit. Very interesting it is...
     

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