Passive P: Tone pot replaced with switch?

Discussion in 'Pickups & Electronics [BG]' started by DDXdesign, Aug 16, 2020.


  1. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    OK so in my current bass project I’m probably going to go with a Geezer P again like in my medium-scale Lightweight Lindert Tribute that GIO and Lowe helped with.

    However, on this bass I want to put a Les Paul style switch on it instead of a tone knob. I’d like it to be full open/dimed in the center position, and then, say, up for half-tone and down for 0 tone.

    Here’s the thing though - I have less than zero idea how to even accomplish this. I assume I’d have to wire a couple resistors into the switch? But that said I don’t know what a typical tone pot’s resistance range is (therefore no idea what the options should be), what the GZR set’s particular tone resistance is, nor, sayyyyyy, even how to identify a switch’s lugs. Or how to solder; everyone says “it’s easy” but it still remains that I haven’t done it. All my wiring jobs on projects (costumes for instance) have used quick connects, wire nuts, or tape, for nothing more than DC motors and LEDs.

    SO, anyone out there that can and would be willing to just kinda... explain like I’m 5?

    Thanks!!
     
  2. lz4005

    lz4005

    Oct 22, 2013
    Get a soldering kit, a multimeter and an electric fan if you don't have one already.

    Practice soldering wires to pieces of metal you have laying around until you're confident you can do it correctly. Watch some tutorial videos. Use the fan so you don't inhale the fumes.

    Then take the multimeter, read the manual, and measure the tone pot resistance you want to duplicate on your existing bass with those pickups in it. Buy resisters that add up to those readings.

    Somewhere in there you should search for a wiring diagram for tone presets. I'm sure one is available. Follow it.
     
    Torrente Cro likes this.
  3. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    A Les Paul type switch will not work the way you'd like. The LP pickup switch is a bit odd, it doesn't fit the normal naming convention for switches, it has 3 positions but only two single sets of contacts. In the middle position, both contacts are closed; the outer positions alternate between having one set of contacts closed and the other set open. You need an open circuit in the middle position for the "tone on 10" setting.

    Your scheme would be simple to do with a 3-position center off toggle switch or a 3-way telecaster style blade switch.
     
    superblues likes this.
  4. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Thanks for that clarification! I certainly hope that someone makes a switch that is physically LP style but that functions center-open like that, just because that’s the switch style and location we’re aiming for.
     
  5. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Well, I have a soldering kit but no wires or metal lying around, and I’m not sure I have time to learn soldering for this project - that said, I will try to find some kind of tone preset diagram at least. Let me pose an example for the moment, then: If your tone pot is, i dunno, 500k, does that mean that for a switching version you’d want 0 resistors in the open position, then 250k worth of resistance at the half position and 500k at the closed position?
     
  6. lz4005

    lz4005

    Oct 22, 2013
    No. There's a capacitor in the circuit, not just the pot value to consider. And you can't assume the change in resistance will be linear. That's why you have to measure it, like I said before.

    If you don't have the time or patience to do it correctly, pay a professional to make it for you.
     
  7. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    I have no experience with this gizmo, but the Free-way switch is a "drop in" LP-style switch with six positions. I'm still a little foggy on it's exact switching arrangement, but it appears to electrically act like two 3-way blade switches, and you could probably wire both sides of the switch the same so it wouldn't matter if the toggle was in the "forward" or "backward" position. It's made in the UK, sold by StewMac and has a "hoo, boy!" price.

    I don't do "pictorial" diagrams, but here's a schematic to get you started. Pickup is on the far left, 3-way tone switch with resistor and tone cap to ground in the middle, then volume control to the right of that, then finally the output jack on the far right. Happy project-ing!
    tone-switch.png
     
  8. JTE

    JTE Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    For the half position, I would get a 250k pot (even better, a trim pot), put it in the control cavity without the shaft being exposed, and wire it up as a tone control. When the build is complete, set the pot to where it gives you the sound you want, and put the cover on the cavity. This gives the person using the instrument the option to tweak that setting..

    For the fully choked position, a 250K resistor switching in to replace the pot might work.
     
  9. MrMoonlight

    MrMoonlight Bottom feeder Supporting Member

    Sep 2, 2008
    Man, you can tell you guys are a bunch of non-guitar-playing mofos...:laugh:

    Gretsch has been doing this for almost forever on their guitars. I own two DuoJets that don't have tone knobs. They each have a tone switch (also known in the Gretsch community as the "mud switch")...and they function exactly the way you're describing. It's a basically a standard Switchcraft leaf switch with the leaves flipped around so the circuit is open in the center position and engages separate tone capacitors in the "up" and "down" positions. Gretsch uses (according to their website) a .0039µf cap for the 50%-rolled-off "up" position and a .012µf for the 100%-rolled-off "down" position.

    toneswitch.jpg

    Obviously, you'll want to experiment with different values for a bass, but the Gretsch tone switch is readily available and does exactly what you want. You can use any switch tip (Les Paul style, Gretsch style, etc) that is has imperial (U.S.) threads.

    Here's a link to one: Gretsch Tone Selector Switch 9221006000 922-1006-000
     
  10. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    That's great! I wasn't aware these existed, that simplifies and cheap-i-fies the OPs project a great deal. :thumbsup:

    I revised my schematic to more closely mimic the actual tone circuit of a p-bass, which does not go completely "open" (infinity ohms) with the tone on "10" - there's always at least 250 k Ohms resistance in series with the tone cap. The schematic shows the switch in the "half tone" postition, which both R1 and R2 in parallel for 125 k Ohms, then the down position which is connected straight to the tone cap for the tone on zero setting. schemeit-project (1).png
     
    Matt Liebenau likes this.
  11. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Oh yeah, if I can't pick up on it of course i'll have more qualified people do it (like they cut me a new nut and nut slot today) but, until the mention of the Gretsch switch above, I was simply trying to determine what the possibilities were, and start planning what I'd have to do - regardless if I could do it with my own two hands or not, I was trying to find out what could be done.
     
  12. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Alrighty! now to try to figure out what anything at all in this diagram means. =0)
     
  13. fermata

    fermata

    Nov 10, 2015
    There are a number of (somewhat different-sounding) ways to accomplish tone up, tone down, and in between.

    For tone up, you can either have nothing in the circuit, which will be maximum brightness (like a no-load pot--the tone control is not in the circuit at all). Or you can use a 250K fixed resistor and a .047 uF capacitor to mimic a tone knob at 10.

    For tone down, you can simply use a .047 uF (or whatever value you like) cap to give the tone control at 0 sound.

    For tone at 50%, there are a few ways to go about it. A trim pot is ideal, because you can dial it in once you've got your switch wired up. (Or measure the 50% setting on your existing tone pot and get a fixed resistor of that value.)

    A different approach is to try a different value capacitor, for instance .022 uF plus a 10K-ish resistor. The resistor will keep the tone from getting honky, and the result will be fewer highs than the fully open setting and more mids than the fully closed position.
     
  14. ChristoMephisto

    ChristoMephisto

    Sep 4, 2011
    A 250k pot rolled back half way is 25k, assuming your pot has 10% tolerance.
    At 6 it would be 70k and at 7 it's 115k
    If you know roughly where you like the pot half way, this might help get closer values to experiment with
     
    DDXdesign likes this.
  15. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Thanks everyone - still trying to figure all this out on the side while working on the rest of the project!
     
  16. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Updated question:

    The way you describe above, it sounds like I could get:
    - No-load: max bright
    - 250K resistor and 0.47 uF cap: Tone open
    - 0.47 uF cap alone: Tone closed

    That sounds like the 10, 5, and 0 positions on a fender TBX circuit, doesn't it? I'm intrigued for sure.

    Also intrigued by the 'different approach' you mentioned for a middy sound.

    Thanks! I may not know how to wire this up, but I can order a switch and some components at least.
     
    fermata likes this.
  17. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    OK one more Q - can either the mud switch or a les paul switch be wired so that no-load/open is "up" instead of center? (realizing the LP switch doesn't have 'open' I would imagine that position would just be wired to the volume pot with no resistors or caps)
     
  18. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    Yes, it's possible with a Les Paul type switch, but the middle will have to be the "tone on zero" setting.
     
  19. DDXdesign

    DDXdesign formerly 'jammadave' Supporting Member Commercial User

    Oct 15, 2003
    Vegas
    Gah! would be nice to just have up be no-cap, middle be 10 tone and down be 0 tone, if I wanted the TBX style sound instead of the 10/5/0 sounds.
     
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