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Wiring question, cap switch for each pickup

Discussion in 'Pickups & Electronics [BG]' started by GlennW, Feb 28, 2008.

  1. GlennW


    Sep 6, 2006
    I'm thinking about putting together a 3-pickup bass with a 4-pole 5-position rotary switch for pickup selection with individual cap switches for each pickup.

    The hot leads of each pickup have their own pole on the rotary switch...I think this will help keep the signals separated.

    I'd like to keep the tone circuits separated as well, but don't know if my plan will work. They'll be on/on/on switches which will give 3 cap value options.

    Here's a picture showing two ways I might try.

    The first one has each cap switch with its own caps, the second way uses the same two caps for all three switches.

    Will these sound the same?

    I'd like to be able to have one pickup bassy and the other trebly.

    If there's no advantage to this I'll probably use another single rotary switch for the caps instead of the three mini-switches.
  2. Koeda


    Aug 21, 2007
    Looks like the caps will end up being in parallel with each other in the circuit so when you select different pickup combinations the tone circuts would change depending on which pu's cap you have swithced on. IMHO the best bet for passive - set up a single tone circuit and switch the caps from there.
  3. GlennW


    Sep 6, 2006
    I think it might work if the hot wires from the pickups go to the cap switches first, and then to the pickup selector switch and then to the jack. I found a few old on/off/on switches and will test this weekend if there's time.
  4. Hey Glenn,
    I'm thinking of doing this as well with individual j-pups and a piezo. What was the outcome? What caps did you choose for the options?
  5. RyreInc


    May 11, 2006
    Kalamazoo, MI
    I have done this exact mod to my Carvin--I have a .022uF cap across the bridge pup, and a .1uF across the neck.

    I really love the sound, full on bridge gets a nice funky, middy kinda sound, very smooth. Full to neck is mostly just bass and low mids, very laid back, good for dub and in general too. :bassist:
    My Carvin has a pan knob, and as I rotate it I can clearly hear the blending of the two caps quite well, and in the middle position is still sounds like a blend of the two, rather than one equivalent cap. This could be because not only does the capacitance change as they are blended together, but the entire impedance seen by the pups changes as well.

    The switching scheme I used is quite simple: one DPDT switch (or two SPDT switches), each channel has the the cap connected to the middle and lower lugs, with the pup negative attached to the same lower lug as well. The pup positive lead is connected to the upper lug. This way the cap is grounded to itself when not in use, and prevents popping.

    Also, you'd only have 2 cap choices per pup with an on/on/on, since one position should have no cap attached (or whatever you want too!).
  6. GlennW


    Sep 6, 2006
    At first I did it with a two pickup bass, a P with a split-P and a Dano RI lipstick at the neck.

    The rotary switches were 6-position and $2.99 at radio shack.

    I used two rotary switches, one for each pickup, and no pots, so the controls look like a stock P. No need for a pickup selector switch since you can turn one or both off.

    The switches went something like:
    1) Off
    2) .1uF
    3) .069uF (.022 + .047)
    4) .047uF
    5) .033uF
    6) .022uF

    How was it? Crowded...10 or 12 caps. All caps were Mallory 150s except the .022s because Mallorys are a lot smaller than OD's.

    It sounded fine, but the "set one to treble and the other to bass" ability wasn't worth it IME. Looks great on paper, but not worth the trouble soundwise.

    So I removed one (used it in a Jazz Bass) and stuck in a different switch (same type) an use it as a pickup selector switch; it goes something like OFF, OFF, lipstick, lipstick + P, P, OFF. The OFF position on the remaining cap switch was changed to "no cap, straight to the jack".

    I'm very pleased with the outcome.

    Mouser is the place to get caps. They have Mallory 150s and Orange Drops in polyester film (225 series) and polypropylene film (715 series) for about $1 or less each.

    The cap switch I removed from the P went to a Jazz.

    Here's what I did to the JB, and I like it:

    Neck V is now a rotary switch for pickup selection (same as on the P, and there's room for a 3rd pickup)

    Bridge V is now a cap switch (as above)

    Tone was replaced with a push/pull pot for series parallel (the pot part is bypassed, but could be used for a master volume).

    It looks stock with the black plastic set-screw knobs.

    If you do that try to find a p/p pot that uses the smaller hole, that way the the little T knob will cover the nut better. The V knobs are big enough to cover the slot in the control plate (made by you) for the tang that prevents the rotary switches from spinning.
  7. Thanks guys,
    Very helpful and the cap info helps me a lot. I'm thinking ahead for my next bass build project. It may end up with DPDT switches instead of rotary switches. I know it won't look stock anymore but I can deal with it. I started another thread specifically for this project "Jazz with piezo bridge and rotary switches"

    Thanks again,

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