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Mixing 250k and 500k pots in a p bass

Discussion in 'Pickups & Electronics [BG]' started by William Cornelius, Nov 26, 2017.

  1. William Cornelius

    William Cornelius Commercial User

    Jan 22, 2016
    So I am knee deep in researching pots, specifically for a p bass. While 250k for a p bass seems the way to go, what happens if you mix 250k volume with 500k tone or vice versa?
  2. Nothing unusual happens, if that's what you are asking. You can use whatever combination of pots gives you the performance and tone that you are looking for.

    A 250k volume pot with a 500k tone pot would be preferable if you want a warmer tone, but a tone control that can be bypassed when not needed. Doing it the other way around would be pointless, however, as the tone control would kill off most of the high end that was preserved by using the higher value volume pot.
  3. William Cornelius

    William Cornelius Commercial User

    Jan 22, 2016
    Thank you so much. So what's your take on using a 250k volume pot with a 500k tone pot, where the 500k tone pot has a variable treble bleed circuit? I am officially out of my depth : )
  4. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    I think you have it backwards. Treble bleeds belong on volume pots.
    William Cornelius likes this.
  5. The best thing to do is use a 250k no load pot. It will give you the useful taper of a 250k pot, plus the bypass setting that people choose 500k pots to attain.

    What do you mean by variable treble bleed circuit? That's exactly what a standard tone control is.
    William Cornelius likes this.
  6. William Cornelius

    William Cornelius Commercial User

    Jan 22, 2016
    Yes, I got that backwards.
  7. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    Treble Bleed is a another misnomer created by Fender, wherein the volume control doesn't cut as much highs when the volume is turned down a bit.
    If you use a 500k Ohm volume pot, you won't have to worry about that.
    William Cornelius likes this.
  8. The treble bleed mod is a popular mod which is done by placing a capacitor between the input and output of the volume pot. When you turn down the volume pot, there is usually a loss of treble, and so the idea is that the capacitor bleeds a little treble from the input through to the output, to put back what was lost.

    You don't need to worry about pots and such. Just decide whether or not it is a feature that you will want.
    William Cornelius likes this.
  9. William Cornelius

    William Cornelius Commercial User

    Jan 22, 2016
    Thank you. I am getting so far away from what I know I did not approach my question correctly. So yeah bypassing the volume control (essentially) in a way that only passes high frequencies from the volume input to the volume output. This while employing some other oddities. I should have done some research before asking my question. So as far as "other oddities" I might be back in a couple days with a much better formed question.

    I did find a good article dealing with bleed values.
  10. Wfrance3

    Wfrance3 Supporting Member

    May 29, 2014
    Tulsa, OK
    mikewalker and William Cornelius like this.
  11. honeyiscool


    Jan 28, 2011
    San Diego, CA
    I use 250k linear for volume and 500k audio for tone on most Fender style instruments to get a brighter sound without changing the resonant peak which happens with 500k volume, while making tone easier to dial in with an audio taper. On some instruments I favor using 300k for both.
    JulienP., Eric ER, PawleeP and 2 others like this.
  12. 40Hz

    40Hz Supporting Member

    Like it. A lot neater looking and easier to adjust the trimpot than doing it point to point.
    William Cornelius likes this.
  13. William Cornelius

    William Cornelius Commercial User

    Jan 22, 2016
    Brilliant. Thanks!
  14. William Cornelius

    William Cornelius Commercial User

    Jan 22, 2016
    Now that is exactly what I am after.
  15. sheltjo6

    sheltjo6 Supporting Member

    Jun 10, 2012
    G&L LB-100 implements a treble bleed capacitor on the volume control.
    William Cornelius likes this.
  16. sikamikanico


    Mar 17, 2004
    It's been a while since I researched treble bleeds, but I think there are 3 common designs - cap only, cap with a parallel resistor, and cap with a series resistor. They all work somewhat differently, and if I remember right the two with a resistor also change the taper of the volume pot (log taper becomes more linear, or actually S shaped). I think the V-Treb circuit may be referring to this effect in that link. Mind you, the control in that circuit is for resistance, not capacitance. Most common application in basses seems to be just a cap (no resistors).

    On pot values, I think it can be useful on some basses to have a brighter tone. I don't see it as necessary on vintage-wound P's, but the overwound or "hot" pickups often sound a little darker, so 500K or no-load pots can help there.
    William Cornelius likes this.
  17. sheltjo6

    sheltjo6 Supporting Member

    Jun 10, 2012
    Mad hatter guitar products have solderless pots you can configure as 250K, 500K, or 750K.
    They also come with different value capacitors you can try out.

    I tried one of these kits out a few months ago.
    They great for experimenting with different pot and cap values, but I would not recommend using them permanently as the wires tend to slip out of the screw down holes.

    My experiments with different pot and cap value combinations just proved what is already posted on Talkbass:
    • higher value pots (500K or 750K) tend to brighten the bass's tone and increase their volume slightly.
    • higher value capacitors .47uF and .1uF tend to roll off more high frequencies as the tone pot reaches 0.
    Here is a link if you are interested is one of their kits.
    Terminator Bass Systems – Mad Hatter Guitar Products
    William Cornelius likes this.
  18. sikamikanico


    Mar 17, 2004
    Can you elaborate on that? I was under the impression that higher level pots increase the resonant peak level, regardless of whether one used them on volume or tone. You seem to suggest the effects are different on volume and tone pots. How are they different?
    JulienP. and William Cornelius like this.
  19. Ric5

    Ric5 Supporting Member

    Jan 29, 2008
    I disclose nothing
    I did that in this bass here with one of my parts basses. I had 2 250k ohm volume pots and a 500k ohm tone pot.

  20. For a volume pot, the pot value affects the resonant frequency of the circuit.

    For a tone pot, all you are doing is varying the resistance in series with the capacitor. So with an audio taper pot, from "0" to around "7" or "8," you are covering the entirety of the range of a 250k pot, but then you have a little bit of extra resistance at the end, to further remove the capacitor from the circuit. For a tone pot, a 500k pot does everything that a 250k pot does, but the 0 to 250k range has to be squashed into a smaller segment of the pot's range of rotation, to make room for the extra 250k to 500k at the end. Since that entire half of the total resistance is swept through in only about one-fifth of the rotational sweep, you really don't lose very much by just sticking to a 250k pot but adding a bypass feature to give you the brightness that is achieved at "10" with a 500k pot. You can bypass a 250k pot in a number of different ways. Fender makes a no load pot that clicks off at the end of the rotation. You can use a push/pull switch to bypass the tone control when you pull the knob up, as well. Or, you can put a dab of nailpolish on the end of the wafer. Or, you can grab an exacto knife and cut the wafer.
    tlite, FugaziBomb and NKBassman like this.
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