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Adding resistors to a potentiometer

Discussion in 'Pickups & Electronics [BG]' started by jive1, Jun 1, 2005.


  1. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Alexandria,VA
    Owner/Retailer: Jive Sound
    I have a 250K stacked pot, and I am looking to install EMG pickups into it. Since a pot is a variable resistor, is there a way to wire a resistor so that the potentiometer value is decreased to 25K?

    Thanks in advance
     
  2. You might be able to use something like a 100 ohm resistor. Thats the logical way around it.
     
  3. eldave777

    eldave777

    May 24, 2005
    I would suggest you buy a 25k pot. They're cheap and after all that's the real "fix".
     
  4. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Alexandria,VA
    Owner/Retailer: Jive Sound
    Yeah, I have a stacked 25K pot on order from EMG, but they are back-ordered and wanted to see if there was a way I could still use my stacked 250K pot for the time being.
     
  5. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    It's definitely possible, I've read previously about such mods to bring a 500K down to 250K but I couldn't tell you the value to use to take it down to 25K
    http://woodmangler.com/Guitar Modification/guitar mod.html
     
  6. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    from my understanding it takes a resistor because a resistor passes a fixed value and a capacitor is variable. I've never looked into it specifically but I'd imagine there's a simple way of figuring it - maybe even from a cross-reference chart. But a 100K resistor sounds logical.

    25K audio pot is one of the few pots available from most music stores, definetly any mainstream like GC/Ash. A stacked 25K is another matter. Probably Stewmac or any of the rest should be able to accomodate.
     
  7. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    In Theory, if you wire a 27.7777777777777777777777 K resistor across a 250K pot, you will get a 25 K pot.

    Now for the real world. I tried this in an electrical simulation program (multi-sim) and the results were very interesting. The result is a 25K pot, but the taper rate of the pot is greatly affected. Basically, you 90% of the change with the first 10% of rotation of the pot. So it works, just not very well.
     
  8. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    Yep, sounds about right. That's usually how theory works. Some unknown variables in the mix.

    ---------------
    A theory doesn't change what a theory is about. (BF Skinner)
     
  9. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    Well here's what is basically happening. Current takes the path of least resistance. When the pot is set at a value below 27.777K, then the pot is the path of least resistance. Once the pot is turned to a value above 27.777K then the fixed value resistor becomes the path of least resistance. There will always be a little curent flowing through each one, which is why you need a 27.777k resistor instead of a 25k one. So the theories are still true, the effects of them just aren't always obvious until you try it.
     
  10. geshel

    geshel

    Oct 2, 2001
    Seattle
    You could stack ten 250k pots concentrically and wire them all in parallel. :D :rolleyes:
     
  11. Funky Doctor

    Funky Doctor

    Aug 28, 2003
    Australia
    You can change the law of the pot easy but it's kinda hard to get the value you want with the taper you are looking for.