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Diagnose my tone pot!

Discussion in 'Pickups & Electronics [BG]' started by CallMeAl, May 4, 2019.

  1. CallMeAl


    Dec 2, 2016
    Ithaca Ny
    I'm trying to figure out if my tone pot is acting as it should or if it needs replaced.

    On the way from 1-5 there is a noticeable volume increase. I definately notice a difference in the treble in this range too. From about 5-10 I can hardly notice a difference, volume or treble. It's a Squier standard Precision, A500k pot, .0683 cap.

    The treble sweep I could live with, it's the volume change that's making me wonder if there's an issue.

    I'm comparing this to my Affinity Precision with newer pots, A250K, .047 cap. On this bass there is a more subtle change in the treble all through the pot's range, but volume stays steady.

    Thanks in Advance!
    Last edited: May 4, 2019
  2. Definitely check the wiring for shorts or bad solder joints, but to me it sounds about right for an A500k and a 68nF in a P. At half rotation, your pot's value will be around 100k. And for an A250K, you'll get that value at around 75%. So with the 500k pot, you are squashing the usable range into a smaller part of the sweep. If you chose the 500k pot for a little extra brightness when dimed, perhaps think about a (250k) no-load pot.

    As for the cap, well, its value is really only relevant once the pot is rolled most of the way down. The cap creates a slight resonant peak with a sharp roll-off above this. The frequency of this peak depends mostly on the inductance of the pickup, so YM will V of course, but with typical P bass pickups, I've found that much higher than 47nF tends to just sound a bit dead. That slight resonance is too low. The volume change you perceive may well be a faulty cap, but it could just be that it is rolling off too low for your pickup and/or speakers.
    alanloomis1980 likes this.
  3. CallMeAl


    Dec 2, 2016
    Ithaca Ny
    Changed out the cap with a new .047. Big difference! Thanks for the thorough reply!
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