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Model J; 500K pots; and what about the tone control?

Discussion in 'Pickups & Electronics [BG]' started by Jim C, Apr 15, 2018.


  1. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    I've had Dimarzio Model J pups in a 74' J bass since the early 90's with the stock 250K pots.
    Have read that going to 500K pots adds some treble and maybe some "air".

    Has anyone had any negative experience with this change?
    Do I leave the 250K tone pot in or change that too?
     
  2. To get the full effect of changing values, change the treble cut pot as well.

    With a 250K Ohm treble cut pot, it's always bleeding some highs to ground, ALWAYS!
     
    Jim C likes this.
  3. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Just out of curiosity, would using a 500K pot on tone and a regular 250K on a stock Fender add treble as well?
    Never heard of anyone doing that before.
     
  4. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    No. Let's be clear. Changing the pot to 500 K doesn't add treble, the signal is already there; the higher value reduces treble LOSS. A 250 K pot allows some of the treble signal to leak to ground; doubling the resistance to the ground side of the pot restricts the signal loss so you retain more of it, whether the pot is a tone or vol has little bearing, the higher value still allows more of the signal to get through. Having two different value pots makes the higher value pot nearly ineffective because the lower value pot is going to cut the signal, so change them both.
     
    Last edited: Apr 15, 2018
    Slater and Jim C like this.
  5. somebrains

    somebrains Supporting Member

    Feb 7, 2017
    Highly depends on the pickup output.
    Bigmans or Fralin 10% overwound J with 500k's ups the rev limiter.
    IE when you are playing soft you are getting the spank and overtones as if you were playing harder.

    Not all pickups will do that with pot changes, and as noted above change the tone pot bc that's basically a catalytic converter.

    If you want to revoice you can add any number of preamps, clips I've heard of the Area J + OBP are particularly growly and cool. You may end up wanting something more civil like Audere. Then again the sound in your head my be a scooped slappy 90's thing so a Bart TCT or Sadowsky fits the bill.

    I'd try pots first, bc those are cheap and answers the uncorking your exhaust issue.
    If that doesn't work what you have to decide if enhancing what the Area J's output Vs a revoice with a preamp.
    You'll find many threads separating those that want enhancement of what's there vs a baked in sound stacked on top.
     
  6. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    I just had a rehearsal and used the J bass with Model J's.
    Hadn't played this bass in ages but wanted to for this project.
    It sounds fine with 250K pots but I ordered 500 to see what they sound like.
    It's always something:

    IMG_8746.
     
  7. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    That pot might be broken.
     
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  8. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    use it for your tone pot, that third lug doesn't get used anyway
     
    Jim C likes this.
  9. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    absolutely.

    raising the value of the volume or the tone will increase the treble.
     
  10. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Of course!
    Thanks Walter
     
  11. 328C8706-DB93-4E04-A357-57132B0A4621. I know this thread is from earlier this year, but I thought I’d post this diagram for the model j from Dimarzio’s specs webpage. Just in case anyone else is just discovering it. Dimarzio says 500k volume, and 250k for tone, but change the cap to .033.
     
  12. I’ve just done this, and tbh, I don’t like the way that the 500k pots do almost nothing for most of their travel then suddenly pour on the gasoline in the last tiny bit of a turn. When I had the 250k volume pots in place, they seemed to roll the volume up or down much more consistently. I didn’t have a .033uf cap, but I did have a .022uf which someone on another forum or post says they like. They are brighter sounding now, although I kind of miss that dark “almost p-bass” sound that the neck pup had with the 250s in place. Rolling back the tone knob doesn’t seem to do very much with the lower value cap in place since it has shifted the control frequency so high. I will try it next with different cap values and the 500k volumes.
    If the controls end up feeling(sounding) too odd to me, I will just change it back to stock circuit with model j’s for that deeper, grittier sound, then get another Jazz bass to load with something brighter.
     
    Last edited: Dec 10, 2018
    Jim C likes this.
  13. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    You may have replaced an audio taper pot with a linear taper pot. What you are describing is how a linear taper pot behaves.
     
  14. They are CTS Audio Pots
    I’ve reinstalled the 250k pots with a pair of .022uf Orange Dops for a total capacitance of .044uf.
    It sounds best to my ears that way.
     

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