Wiring Q. Is it possible to...

Discussion in 'Pickups & Electronics [BG]' started by Thebiggestjerk, Jul 15, 2017.

  1. Thebiggestjerk


    Mar 29, 2017
    Is it possible to remove a tone pot and replace it with either a DPDT switch or a push/pull pot with an integrated capacitor so tone gets turned fully down with the flick of a switch?

    If so would someone mind please drawing me a diagram?
  2. 40Hz

    40Hz Supporting Member

    May 24, 2006
    You might try installing a "varitone" circuit - which is basically a rotary switch with 6 (or more) different capacitor values to give you a broad range of different tone options.

    You can install a prebuilt version. The one sold by Stellartone is the best known. Or you can build your own very inexpensively. It's a simple enough circuit. Google "bass varitone" to find dozens of different schematics.

    Here's one example of a simple varitone:

    Spidey2112 likes this.
  3. Thebiggestjerk


    Mar 29, 2017
    Thanks for the idea, but I have one cap that I REALLY like the sound of when it's "dialed off" .... totally Jaco.

    This is an on stage bass so "simple" is a must. Just need on and off. Has one volume knob and that's it. Both P's and the J are wired together in series.
  4. If you just have one vol and no other controls, then yeah get your hands on a push-pull pot so you don't have to drill any extra holes. It will have a DPDT switch, but you'll only need two lugs. IOW, a SPST switch will do what you want.


    When you pull up, the top two lugs short, connecting the cap to earth. This is electrically identical to a tone pot turned all the way down.

    To keep to one hole, FWIW, you could also use a stacked pot with vol on the top and tone underneath.
  5. Thebiggestjerk


    Mar 29, 2017
    Thank you sir. Do I still need to ground one of the outside lugs to the back of the pot?
  6. No need. Take the earth wire from the pot and the earth wire from the pickup, twist together, then solder them to the sleeve lug of the jack.

    Earthing the pot casing will help (very slightly) with RF shielding, but I recommend against soldering up to pot casings if you can avoid it. Copper tape or some shielding paint will work fine to earth the pot for shielding purposes.
    ex-tension likes this.
  7. Thebiggestjerk


    Mar 29, 2017
    Would this setup still be compatible with the treble bleed circuit (.0012mF cap, 130kv resistor) I have wired in series from the wiper to the output lug?
  8. Sure, but there won't be any treble left to bleed with the switch pulled up... ;)
  9. Thebiggestjerk


    Mar 29, 2017
    This worked amazingly well, thank you!!! Both modes work perfectly. I used 2x .047 microfarad caps wired in parallel (which is 0.094 out the door) which makes for a nice reggae tone; also the treble bleed works perfectly in both modes- volume stays nice and even without all balls falling out when the volume is decreasing.
    ctmullins likes this.
  10. nice one mate...
  11. Thebiggestjerk


    Mar 29, 2017
    Now let's say that I wanted to have the bridge pup on this anti-tone circuit?
  12. not sure what you mean... if your pickups are wired in series, the volume and tone controls will work on both pickups together.
  13. Thebiggestjerk


    Mar 29, 2017
    I will separate the pups back to individual wirings. Just want both now on the same pot but only the bridge attached to the cap when when pulled.
  14. are the pickups staying in series, or going back to parallel?
  15. Thebiggestjerk


    Mar 29, 2017
  16. Honestly, taking the tone off one pickup and not the other while they are summed in parallel is kind of an odd thing to request. Without actually tapping the pole pieces with something steel, I doubt you'll hear by ear which pickup has the tone off. But anyway, you'll need a couple of resistors to isolate the tone cap to just one pickup. I've wired similar circuits, but not this exactly, so I'll say a resistor pair around 10K-22K should work. You may need to experiment though. Too much resistance, and you'll start to lose signal and treble, too little and your tone cap will roll treble from the P as well.

    The switch shorts the resistors when down, so I'd leave the cap out at first. You'll be able to directly compare the sound with and without the resistors. I'd actually use a 100K or 50K dual gang linear pot as the resistors so you can find the sweet spot where you get isolation before you get signal loss. As I mentioned, you'll have to tap the polepieces to hear the isolation working when you do install the cap. I doubt you'll be able to set this be ear. Then remove the dual gang pot, measure its resistance, and put in a pair of the fixed resistors of the closest value. And FWIW, I'd recommend trying a few different caps.

    Last edited: Jul 18, 2017
  17. OT, but I just noticed that this circuit is not quite right. I'm not trying to be a smart-arse, but I presume the switch is pictured from the bottom/lugs view. So then this will work anti-clockwise. Turning the control clockwise will actually make the bass's tone darker.

    And also, the caps should really be connected to the outer lug - the pickup side - of the volume control. At full vol, there's no difference, but as you wind back the vol, you will be puting resistance between the pickup and the cap. This is just what a standard tone control does. So your volume pot will also be a tone pot. Even more than usual! That will damp the little resonant peaks you get from having each cap directly across the pickup.