Looking for a volume pedal with a 47K-50K log potentiometer

Discussion in 'Effects [BG]' started by San Diego, Jun 29, 2008.

  1. San Diego

    San Diego Supporting Member

    Oct 30, 2005
    San Diego
    I've got a preamp with a volume jack on the rear panel and I'd like to see if I could use it to control the volume and also use it as a standby. According to the manufacturer, the value of potentiometer which would work best in a volume pedal would be 47K-50K log. So far, I've been unsuccessful at finding one. I've seen potentiometer values of 500K, 250K and 25K, but nothing in the range I was looking for.

    I thought that I could get an old style Ernie Ball pedal, without the circuit board, and find a 47K-50K potentiometer that would have a long enough shaft and try to get it to work, but really that's just an idea and I don't know if it would work.

    So, I thought I'd come here to ask if anyone knows of a solution for this. Another idea is to get an on/off switch type of pedal to toggle the volume. Again, I'm unsure of the type of switch I would need.

    If anyone knows of a pedal that would work or another solution that would be great. Any other thoughts would be appreciated as well.
  2. Is what you're hoping to do any different to just having an off-the-shelf volume pedal in the circuit after the preamp?

    Seems like you're putting a lot of effort into a volume pedal modification so it works like... a volume pedal!
  3. volume pedals are pretty much just a pot in a box so go for it if you wanna swap one out
  4. True, but not all pots are made alike, and the ones in EB VP Jr's, for example, have an abnormally long threaded shaft which is difficult for us mere mortals to obtain replacements for.
  5. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Strange, I seem to get the abnormally long threaded shaft all the time, usually from my boss.
  6. San Diego

    San Diego Supporting Member

    Oct 30, 2005
    San Diego
    True, I could use the 250K volume pedal that I have now, but with the correct pot, I thought I could get the volume to swell. Currently the pedal acts like an on/off device. I was wondering if anyone knew of a volume pedal with a 47K - 50K pot. The on/off function is okay, but I'd probably go for a foot switch for the toggle rather than a volume pedal.

    The preamp is the Phil Jones P-1 and on their website they have advertised that the volume jack is compatible with the Phil Jones volume pedal, however, after a few emails I got the impression that they do not have a volume pedal in the pipeline. But, Phil did give me the proper value for the potentiometer that would work best for the P-1.

    The build-your-own idea is good, but finding a potentiometer that will fit a pedal and bypassing any of the pedals internal circuitry is a bit tricky, at least for me.

    So, I was trying to find a pedal that matched or if someone has built one before that works well, I could use some advice.
  7. scotch

    scotch It's not rocket science!

    Nov 12, 2006
    Albany, NY USA
    Please see Profile for Endorsement disclosures
    Cheap expression pedals are easy to modify with various short-shaft pots. Like BeSpeco, etc...

    I've also seen techs modify the value of an existing pot with different combinations of resistors. I'm no engineer, but this solution might work?
  8. I wouldn't be so hung up on getting the exact value. I'd say a 25k might work just as well as the recommended value, but that's only an educated guess.

    What I was suggesting was just to ignore the volume jack on the preamp and just put a volume pedal in series with the normal output signal. I just can't see what advantage this mystical volume jack has over a run-of-the-mill volume pedal.
  9. San Diego

    San Diego Supporting Member

    Oct 30, 2005
    San Diego
    Thanks Niftydog & Scotch,

    I suppose I could just use a regular volume pedal in-line to the preamp, but I was tryin' to get a standby feature by using the preamp volume jack which controls the master volume to the amp. This way I could still use my tuner in silent mode and ensure I'm not popping when changing basses.

    I'm still just using the volume knob on my bass as my in-line solution.
  10. Well, I'm advocating the volume pedal after the preamp, then you retain all of those features, don't you?
  11. San Diego

    San Diego Supporting Member

    Oct 30, 2005
    San Diego
    Sure, now I understand, just never did that before. With the signal from the preamp to the amp being line level, I'm thinking my 250K potentiometer will act like an on/off pedal, producing no swell. But seeing as I've never tried this, I'll check it out.
  12. It's really got nothing to do with the amplitude of the signal - it's all about the impedances involved. The impedance at the volume pedal jack seems to be significantly different (high?) to what I would expect at the normal signal output jack (low).