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Question about Dimarzio style Jazz humbuckers (model J) and tone caps/pots

Discussion in 'Pickups & Electronics [BG]' started by bobbycas11, Nov 15, 2017.

  1. bobbycas11


    Jul 15, 2017
    CT, USA
    Hello everyone,
    I searched on here for answers about this and didn't find any, so I don't think this is a repeat post but if it is I apologize. I have a 2017 MIM Jazz bass that I love and I love upgrading it almost as much as playing it. So after doing the tuners/nut/bridge I tackled the electronics. I threw in a pair of Dimarzio model J's which are the split coil noiseless humbuckers. I didn't know what to expect from them but they do sound like single coils with a little extra low-mids added which is nice.

    Anyways, when I put these pickups in I also replaced the entire wiring harness with an Obsidian wire solderless kit for Jazz bass, which is awesome because I like soldering and all but it's nice to avoid it. That came with a .047 Russian paper in oil capacitor and 250k pots like any normal Jazz bass would. My question is since these pickups are split coil humbuckers, would they benefit from having 500k pots? Especially wondering since they're a little bit darker than the originals (though they don't sound too drastically different).

    Also, does anyone have experience with using different tone caps on a Jazz bass, either with single coils or split coil humbuckers like I have? I see all sorts of videos and articles online about using various tone caps ranging from .022 to .1uf for P bass, but not much about Jazz basses. I experimented with a few different kinds on my P bass (Squier VM Jaguar Special that I upgraded everything on and converted to be fully passive, and found the .1 to be too dark for me but a .068 was perfect so I kept that in.) Basically I was wondering about putting a smaller value cap in, maybe a .033 or .027 or even a .022. If anyone has any experience messing around with different tone cap values in a J bass I'd love to hear about it! As well as any experience using 500k pots with split coil humbuckers such as Dimarzios, or Seymour Duncan Apollo jazz, or any of the other split coil humbuckers they make for jazz bass.

    Thanks a bunch guys!
  2. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    Everything can benefit from having 500k Ohm pots.
    If you like the timbre of the bass with the treble cut (tone pot) rolled all the way back, then keep the capacitor value you have, but I'd ditch the paper in oil cap.

    If you think you'd like it even darker when it's rolled all the way back, get the 100 nF (0.100 uF) cap.
    If you would like it brighter when it's rolled all the way back, get a 22 nF (0.022 uF) cap.
    Last edited: Nov 15, 2017
    mbelue and bobbycas11 like this.
  3. The effect of different resistances is subtle. You would shift the resonant frequency of the pickups up by a tiny bit with 500k pots, giving a bit more clarity. I wouldn't bother swapping pots unless there was a problem with the current pots that necessitated having to replace them.

    Capacitance for a tone control is analogous to adjusting the frequency knob on a parametric equalizer. Capacitors are cheap and easy to play with, so it is usually best to get an assortment of different capacitors and try them all out. A good way to experiment is with alligator clips, so that you don't have to solder until you have made your final choice.
    Axstar and bobbycas11 like this.
  4. bobbycas11


    Jul 15, 2017
    CT, USA
    Thanks guys! Question, when you say everything can benefit from 500k pots, do you use them on a normal J or P bass with single coils? If so it's not too bright? Never had anything beside 250k pots for my basses, but I've heard others say 500k pots on a J or P with standard pickups is too bright/snappy, but if you have experience with this then it's worth checking out. Especially since the pickups are now split coils instead of true single coils, I was wondering since generally people suggest 250k for single coils and 500k for humbuckers whether these Dimarzio Model J's would be considered humbuckers or single coils for the purposes of pot selection. They are slightly darker than the stock single coils
  5. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    I guess it's a personal preference, but I'd rather an instrument be too bright, because then I can just use the treble cut knob.
    If it's not bright enough, not much you can do, unless you're working with an active bass.
    mbelue likes this.
  6. Don't worry about what people say. Find your own preferences.
    mbelue and Axstar like this.
  7. Zoobiedood

    Zoobiedood Commercial User

    Sep 1, 2015
    Writer/Ambassador/Artist/Resident Bass Expert for Seymour Duncan
    Well, the Apollos with 500k pots are my current favorites...
  8. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    Just as a hypothetical, I did some calculations in a RLC resonant frequency calculator:

    three 500k Ohm pots in parallel = 167k total resistance
    treble cut pot with a 22 nF cap rolled halfway back would give you 11 nF of capacitance
    just guessing on the Henries (inductance) of a Jazz pickup, but in the case of full humbuckers they are twice as many Henries as a single coil pickup of an identical coil as the humbucker is using
    In other words, if you measure only one coil of a humbucker, it would have half as many Henries as both coils of the humbucker in series.

    So, let's pretend like we have two single coil pickups in a V/V/T config:


    The resonant frequency is over 1 kHz, perfect if like a mid-forward sound.

    Now, we change those to humbuckers & double the Henries:


    The resonant frequency dropped quite a bit, but would have dropped even further if you're using 250k Ohm pots (which would present only 83k Ohms of resistance in parallel).

    Disclaimer: bear in mind that this isn't real world, for instance:
    the resistance is going to vary & this calculator isn't set up to calculate a circuit of the exact same configuration as in the bass
    Those split coil humbuckers aren't going to double the Henries like a full-sized humbucker.
    It is still a pretty good indicator of how a humbucker can drop the resonant frequency.
    Last edited: Nov 15, 2017
  9. I added the Dimarzio DP126 "noiseless" set to my Squier Jaguar VM Special (long scale) bass (which includes their "Model J" PUP, and reached out to DiMarzio tech support for volume & tone pot value recommendations. They recommended 500K of the vol pots & 250K for the tone pot. I installed same, and experimented with the tone caps, ending up with 0.022 uF for the cap. I had used an inline selection of jumper'd caps and a 250K tone pot on the bass output at first, but the buffered bass boost preamp output made that a non-starter. I switched to lifting the existing tone cap and jumpering different values in on the INPUT side of the bass boost (which I rarely use anyway), which allowed more effective testing.
    The 500K pots did reduce the amount of treble bleed to ground (both to my 67 year-old ears AND using a B&K spectrum analyzer - I'm a retired E.E. with residual "toys", but I admit that I miss my NASA-certified "soldering minions"), and the 0.022 uF cap did sound the best to me (tested 0.1 to 0.01uf to determine that).
    FWW... I also tested 1 Meg Ohm pots, but saw little advantage to them over the 500K.
    Also, as with my guitars (Gretsch, Gibson, Squier) humbucker-eguiped guitars, I strongly recommend the use of treble bleed circuits on bass (assuming you need the lower-volume tone consistency.
    Your mileage may vary...
  10. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    I bought a pair of Model J's in the late 80's.
    Either I didn't read the instructions, or back then they didn't recommend 500kOhms.
    It's a 74 Jazz bass and I've never felt it was dark sounding with 250K's and the stock cap.
    In fact, it became a studio bass for awhile and recorded beautifully.
    I've had a stock 72' at the same time and mostly prefered the Model's J over single coils.
    For live use I did too for probably 25 years, but now prefer the stock single coil.
    With a decent amp, either can sound great.

    I have a pair of Fender 55's to try but back to playing a P (Sandberg with mild EQ).
    Funny how types and tones of instruments change over time also between studio, stage, home, etc.
  11. Primary

    Primary TB Assistant

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