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EMG active p-bass pups... why not 500k?

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


  1. ::::BASSIST::::

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

    Sep 2, 2004
    Vancouver, BC Canada
    Just got a set of EMG active p-bass pups. The instruction sheet says use 250k pots only. Why? The bass is a shortscale and can get muddy. If I used a 500k that would make it that much clearer. I like a really clear sound. But since the emg instructions say not to use anything but 250 I am apprehensive. I am even thinking of trying a 1 meg pot.

    Also, what happens when active pickups' battery dies? Does it sound like some wierd distortion? That's what happened to me last night at band practice. I am hoping its the battery, I am pretty sure it is, and not something more serious.

    thanks in advance!
     
  2. RevGroove

    RevGroove Commercial User

    Jul 21, 2002
    Burlington ON Canada
    Manager, Account Services: Long & McQuade Ltd. (Burlington); MTD Kingston Basses International Emerging Artist; Bartolini Electronics Emerging Artist
    Actually, if those are active pickups, you mis-read the instructions...it's a 25K put you're looking for. I'm not sure what would happen if you used a 250-500k pot instead...the passive EMGs use 250K pots...
     
  3. ::::BASSIST::::

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

    Sep 2, 2004
    Vancouver, BC Canada
    Dang! You're right! I put in a 250k it sounded okay. Now I am curious what the 25k will do to the sound.
     
  4. fookgub

    fookgub

    Jun 5, 2005
    Houston, TX
    I've always wondered about this, too. EMG's website says 250k and 500k pots act more like "switches" with their active pickups. But a pot is just a voltage divider. Provided the impedance of the pot is much greater than the source impedance of the pickups, there should be little difference between different valued pots (other than higher impedance circuits being more susceptible to noise pickup).

    Ideas, anyone?
     
  5. elros

    elros

    Apr 24, 2004
    Norway
    Proprietor, Helland Musikk Teknologi
    From the EMG bass pickup datasheet:
    A higher ohm value on the volume pot won't affect the sound as it does on passive pickups. The EMG pickups are active and have a 10kOhm output impedance. As I understand it, that is a non-reactive output (being active) and so a resistive load (like a volume pot) won't change the timbre of the sound like it will on a passive pickup (which is basically a coil and will act as an LR filter together with the volume pot).
     
  6. fookgub

    fookgub

    Jun 5, 2005
    Houston, TX
    I doubt the EMG's have a 10k output impedance. If they're using 25k pots, it's probably more like 1k or 2k. I agree with pretty much everything else you said. Passive pickups have rising impedance with frequency, which is (one of the reasons) why rolling off the volume cuts treble, too.

    I suppose they just want you to use 25k to minimize induced noise.
     
  7. elros

    elros

    Apr 24, 2004
    Norway
    Proprietor, Helland Musikk Teknologi
    I was actually expecting around 1kOhm too. But the spec sheet said only the DC and CS models are 2kOhm, the others are 10kOhm. Here's the spec sheet.
     
  8. fookgub

    fookgub

    Jun 5, 2005
    Houston, TX
    hrm... I find that a little odd. I wonder if the spec sheet is right...