active pickups specify 25k... why not 500k?

Discussion in 'Pickups & Electronics [BG]' started by ::::BASSIST::::, Oct 29, 2005.

  1. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    I have a set of EMG active pickups. The instructions say only use 25k pots. Why couldnt i use a 500k pot? I omit the tone pot so I only have the one volume pot.

    My goal is to get a clearer tone from my shortscale SX p-bass.
  2. mahrous


    Aug 13, 2005
    to not resist the circuit and current of the high output of ur active EMGs.
  3. What EMG pickups do you have? They usually come in a set with everything prewired, so it is basically plug and play. Did you buy them used or something? Older model?
  4. fookgub


    Jun 5, 2005
    Houston, TX
    Sorry, but this is not correct. I believe EMG specifies 25k because their pickups are capable of driving a 25k load, and they want to take advantage of the better noise immunity of lower impedance circuits. I don't see any reason why 500k wouldn't work... it's just not optimal.
  5. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    I bought the EMGs used, but they seemed to be the newer variety. They were already soldered to the pots and everything. I guess I'll try soldering in a 500k pot and see what happens. Just wondering why they would say only use 25k... like something might not work properly if you didnt follow their advice. Noise issues is probably right on the money.
  6. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    According to popular knowledge here you will make your pickups brighter. I think that's wrong and I'd predict with a 500k pot you'll mess up your curve and you'll find a spot in the rotation where a tiny turn takes it from on to off and about 90% or more of the rotation will be worthless. Let me know what results you get.
  7. A9X


    Dec 27, 2003
    Sinny, Oztraya
    That's for passive pickups, not those with an active buffer built into them and a constant output impedance wrt frequency.
    Nope. You're describing the effect of a linear pot, not the usual log/audio taper. The 25k pots are likely specified for the reasons fookgub outlined in an earlier post.
  8. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    Uh, no & no. :)
  9. SeamanTickles


    Mar 23, 2014
    Yeah I agree with moo. It's what it says on emg website. And the pot has nothing to do with the buffer, it's after that point in the circuit, therefore it will indeed make it brighter. Imho.
  10. SeamanTickles


    Mar 23, 2014
    Sorry to bump a thread though.
  11. The reason that 25k pots are used with active pickups is that they have a lower output impedance than passive pickups. If you try to use high value pots, the effect is going to be that the pot will quickly mute the output as it is rolled down, because the series resistance will be so great, in comparison with the impedance.
  12. Joospocks


    Jul 1, 2010
    If only SeamanTickles had waited a year and a half longer to post in here, it could've been a ten year old zombie thread bump. Too bad. :p