Wiring & shielding P/J Bass VVT

Discussion in 'Pickups & Electronics [BG]' started by Dr Dan, Mar 17, 2016.

  1. Dr Dan

    Dr Dan Supporting Member

    Apr 12, 2011
    Hi everyone. I'm building a '51-style P-Bass with a Fralin 51P single coil in the neck position and a Dimarzio Ultra Jazz split-coil (series) in the bridge position. (Yes, I am aware that I will get single-coil hum from the neck pickup. I want an SCPB & I can live with the hum.) It has a metal control plate, with a side-mounted output jack, i.e. jack is not in the control plate. I'm using mini pots due to tight space in the Tele-style control cavity. I've done some research & come up with a wiring scheme that I think will work, but as I'm new at this I wanted to see whether anyone can spot any problems with it before I start.

    * I'm planning to run a straight, bare ground wire to daisy-chain the pots, soldered to the back of each pot and soldered through the ground leg of each volume pot.

    * That daisy-chain wire would continue past the tone pot to a lug mounted in the wall of the control cavity, along with ground from bridge and a ground wire between the control plate and body. One ground would run from the lug to the output jack ground terminal.

    * The control cavity and pickup cavities are all shielded with shielding paint. The lug would ground the shielding.

    Am I making any mistakes I'm not seeing? I've attached a schematic. Thanks for your help!
    Bass wiring.jpg
  2. Dr Dan

    Dr Dan Supporting Member

    Apr 12, 2011
    Further question: since the pots are being attached to a control plate, as long as the control plate is grounded, is there anything to be gained by running a ground wire across the pot casings?
    Jazz Shielding Pictorial (Big Images Warning)

    Not having to solder pot casings (& risk overheating) would be fine with me!
  3. There is a lot to be gained! Firstly, using the control plate to ground the pot is a technique done to keep costs low in a production-oriented environment. It's not ideal, and anyone wiring their own bass should do a better job. When you rely on a mechanical connection, instead of a soldered one, you can have intermittent continuity problems when either a pot works loose, or the connection corrodes, over time. You want to use a proper soldered connection to avoid this problem. Secondly, many people find it preferable to solder a thick piece of solid wire across the backs of the pots, to prevent the pots from rotating, if one of them should work loose.
    Dr Dan likes this.
  4. Dr Dan

    Dr Dan Supporting Member

    Apr 12, 2011
    Great! Thanks.

    In that case, do you think I'd be good to go with the original schematic above?

    Also, any advantage to moving the pickup grounds off the pots (legs) & onto the lug?
  5. The diagram is fine.

    There would be less risk of damaging the pots when soldering.
    Dr Dan likes this.
  6. Since you are using two single coil pickups from different manufacturers, it's important to have one with north magnets and the other with south magnets so that you can wire them to hum-cancel. I'd email the pickup companies.
  7. Growlmonkee


    Jan 30, 2013
    Florida, U.S.
    The only thing not shown, I can think of, (you probably have already), is that all the conductive painted cavities need to be connected to common ground, (more difficult with paint if there are wire tunnels between cavities), but it can be done. @ Robbie, it's a single, and dual coil.
  8. Antisyzygy


    Dec 8, 2014
    Jess L. makes a hum-cancelling '51 pickup : P-bassĀ® 51 coil-split Tele-bass

    That one is affordable. I tried a Fralin Split 51' and it sounded roughly the same as the single coil 51' with a bit more low-mids. The character was still there, it just kinda re-EQ's it to have some more low-end.

    Anyway, it sounds like you didn't want anyone to comment on the hum-cancelling ;)

    The schematic looks good.

    When I shield I just run a wire from the back of a pot to some copper foil in the body. I usually don't solder the wire to the copper foil, I just grab another piece of copper foil and secure the end of the wire down. That should work with conductive paint as well, but the alternative is you solder an eyelet on the end of the wire and then use a screw to bolt it down to the conductive paint.
    DiabolusInMusic likes this.
  9. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    I can assure you it does. I did this to a friend's bass to see if it would work and he has yet to call me to fix his bass, this was 2+ years ago.
    Antisyzygy likes this.
  10. Dr Dan

    Dr Dan Supporting Member

    Apr 12, 2011
    Yeah, my plan is to run a wire from the lug in the control cavity to the output ground. I've checked the pickup cavities and when the control cavity is grounded, the pickup cavities are grounded as well. So grounding the central lug should ground the cavity, & thus the pickup cavities too.
  11. oops. yep the ultra jazz is a humbucker. my apologies...

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