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Crazy idea? Blend knob for coils on P Bass pickup

Discussion in 'Pickups & Electronics [BG]' started by estesbass, Dec 16, 2013.

  1. estesbass


    Dec 6, 2004
    Nashville, TN
    One of the coils went out the other day on my 71' P Bass during a gig. The volume obviously dropped to half - but the resulting sound was interesting -- really aggressive and thinner (in a cool way).

    I'm sending it off to be rewound, and, in the meantime, it got me thinking...has anyone ever put a blend knob (or separate volumes) on their P Bass - so that you can control each coil separately?

    I'm assuming that there would be a hum - but it could be a useful studio tool for getting some different tones.

    I ran the idea by my luthier and he said it would be simple to do - but he had never heard of anyone doing it.
  2. You would end up with uneven string response. That's not useful at all, unless you can find a way to adapt your playing to make that musical.
  3. Plucky The Bassist

    Plucky The Bassist Bassist for Michael "Epic Mic" Rowe

    Jul 30, 2010
    Houston, TX
    Yes, this might work better for something like a Musicman or G&L-style humbucker. With one of them off, you'd be missing quite a bit from the other two strings.
  4. RobbieK


    Jun 14, 2003
    Yes, a crazy idea. A blend pot won't get you the sound of a broken pickup. Plus the blend pots on the market don't really blend passive coils properly. Plus if you wired, say an MN pot - the most common choice for blend - your pickup coils are now in parallel instead of series. That would really change its tone, even with the blend bang in the middle. Not to mention the stuff everyone else has said about string balance.

    For a thin sound, what about a switchable passive high pass filter? like the fender jag has on one of its switches...

    I've also heard of guys running a switch to send each coil out a separate send, so you can use different effects on two strings and not the others, or play octaves from different amps etc...
  5. Not true. When blend pots are used with series-wired pickups/coils, each gang of the pot varies the impedance parallel to each coil, with no modification to coil wiring, and no reference to the ground potential. Think of it like shorting each coil, rather than doing a voltage-divider circuit.
  6. RobbieK


    Jun 14, 2003
    ^^ ahh true. Good point. I didn't think to wire one like that.

    I still think it would be best to try a simple high pass for that thin sound. Try a few series caps and a shorting switch. Without an active buffer for a constant load, the switch will be a little unpredictable with different amps etc, but worth a try.

    Or try a phase reversal switch on one of the coils. I've never tried this with a p pickup, but I don't think it would be too thin as the coils are on different strings. It would hum a bit though...
  7. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    +1, a busted coil is nothing like a blend pot.

    all the blend pot would do is turn two strings down.

    the "busted coil" sound (choked-off low end) could be done with a cap. G&L instruments do this, with a bass-cut knob that sends the signal in series through a small cap like an .002μF to kill the low end.

    (remember, that P-bass pickup is in series, so the one busted coil kills the lows from both coils.)
  8. kohntarkosz

    kohntarkosz Banned

    Oct 29, 2013
    Edinburgh - Scotland
    I've had a pickup do that. The aggressive and thinner tone is the result of an open coil, and wouldn't work with your wiring.

    I have a Cort bass purely for sandboxing. I wired the split P pickup a few different ways. One wiring scheme had a kill switch for the D-G half of the pickup. As the bass was a PJ it sort of worked. I had it wired in stereo, so the E-A half of the P pickup went to one output and the full J pickup went to another pickup. I could also split this to dual-mono...
  9. petrus61

    petrus61 Supporting Member

    You could simply install a push pull pot to sect between two caps. The normal .1 or .047uf, and a .01 or .022 for shunting less high end to ground. This or a series/parallel would be much more effective. The split single coil is still a single coil, so it wouldn't be productive to screw with it by somehow splitting it.
  10. kohntarkosz

    kohntarkosz Banned

    Oct 29, 2013
    Edinburgh - Scotland
    I don't think OP was after this sort of solution, as graceful as it is. OP seems to have liked the ragged tone he got when half his P-pickup went dead. From personal experience this tends to make the pickup sound aggressive, if slightly lacking in bass end response. Geddy Lee had/has a pickup like this on his original pawn shop Jazz, and Roy Buchanan may well have had the same 'problem' with his Telecaster's bridge pickup, giving him a unique tone he is quite well noted for.

    OP could mess around with caps in series, rather than parallel, with the original pickup.
  11. estesbass


    Dec 6, 2004
    Nashville, TN
    Thanks for all the replies. Yes - what I'm after is the ability to get that "broken coil" sound...a kill switch would be perfect. But possible?
  12. RobbieK


    Jun 14, 2003
    desolder the hot wire from the output jack.

    put a capacitor where the connection was - one lead to the jack, one to the hot wire.

    wire a (spst) switch across this cap - one lug to the jack, one to the hot wire.

    when the switch is on, the cap is shorted out, and the bass functions as normal.

    when the switch is off, your signal goes through the cap.

    I'd start with a 0.0047 uF (4n7) greencap. If it's too thin, double the value (0.01uF - or 10nF), if it's too deep sounding, halve the caps value (0.0022uF - or 2n2).

    Keep halving or doubling the cap's value 'til you get the funk.

    Enjoy crazy thin, clunky bass tone! :bassist: