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Pot Resistance Values on Tone?

Discussion in 'Pickups & Electronics [BG]' started by Means2nEnd, Feb 21, 2013.

  1. Means2nEnd

    Means2nEnd Supporting Member

    Have been wanting to post this question for a while but didn’t want to look stupid. Just checked the mirror and it doesn’t matter either way…

    This is for the potentiometer gurus out there...As far as the effect of the tone and volume of a pickup active or passive when run through a balance or volume pot at say 250K for passive and 25K for active the number is a measurement of resistance and I hear how lowering the value will cut high end and darken tone somewhat. Is this for both passive and active? My thinking is if the value is decreased wouldn’t that increase what goes through the pot on its way to tone pot or preamp. My thinking tells me the opposite would happen contrary to what I read all the time. Why when there is less resistance cuts signal or decreases spectrum?
  2. Volume pots do two things when you roll them down; increase series resistance and decrease parallel resistance. A lower value pot sounds darker because the maximum resistance parallel to the signal path is lower than that of a higher value pot, and thus, the signal encounters less resistance as it bleeds off to the ground potential. Why don't you just use a high value pot and roll it down to taste when you want a darker sound? That's where the series resistance becomes significant. If a pot value is too high for the signal impedance, it will present a significant resistance that opposes the flow of electrons from the input to the output, very early in the rotation. So if the pot value is extremely high, rolling the volume down a hair will kill all the output, but if the value is extremely low, the signal will be loaded down all the time. However, if you stay within an appropriate range, you can play with values to taste. High impedance signals, like that of passive pickups, tend to work best with 250k or 500k pots, while low impedance signals, like that of active pickups or preamp/buffer outputs, tend to work best with 10k, 25k, 50k, etc.
  3. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    hadn't thought of it that way, and it makes tons of sense; awesome!

    TL;DR version for the OP:

    pots are in parallel, going between hot and ground; the higher the pot's resistance, the less signal "gets through" it from hot to ground and gets lost.

    the very highest resistance pot is no pot at all, so nothing gets lost through it.
  4. Means2nEnd

    Means2nEnd Supporting Member

    I think I’m following you correctly. Too high or too low will have almost the same effect on tone due to the two different types of resistance. Being in the correct range for the pickups themselves will ensure good open tone through the change of the pot up to down. SO here is my next question what parameters from the pickup company does I look for to help put the right resistance value pot to the pickups?

    I work with active EMG pickups a lot and most times 25K is the norm but the Seymour Duncan preamps use a 100K pot in the balance and a 10K for the master volume and it works well most of the time. I wondered what switching the balance pot to a 25K balance pot would do the overall tone with say their standard active jazz pickups...

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