Change a pickup's resonant frequency and tone with a loading capacitor

Discussion in 'Pickups & Electronics [BG]' started by fermata, Mar 3, 2022.

  1. fermata

    fermata Guest

    Nov 10, 2015
    The two posts below by @micguy are so fabulous, I'm popping them into a new thread, in hopes that they can more easily be discovered.

    For context, the pickup(s) and related components form LCR circuits, which means changing any of those parameters (inductance, capacitance, or resistance) in a passive bass changes the instrument's tone. A dramatic change comes from adding more capacitance to the circuit, and it's very easy to accomplish (just add a capacitor between the pickup hot lead, where it connects to the volume pot, and ground).

    Basically, with an inexpensive capacitor and a few minutes of soldering, one can accomplish tonal changes akin to swapping pickups or wiring (and it can be made switchable). The concept only surfaces from time to time in this forum, but it's so easy, cheap, and effective, that it deserves to be a go-to when talking about pickup/tone mods.

    One more note, it's easy to test out different capacitor values without popping the hood (keep the volume and tone controls at 10): unscrew the barrel of the instrument cable where it plugs into the bass; attach one alligator clip lead to the cable's hot tab; attach another clip lead to the ground tab; clip a capacitor between the free ends of the clip leads to hear how it affects the tone; try different values and then hardwire in the one you like.

    Last edited: Mar 3, 2022
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  2. SteveCS


    Nov 19, 2014
    Hampshire, UK
    My pseudo-passive* PJ has a multitude of options. It has 2 caps that are available in 3 combinations - a 'big' one', a 'small' one and 'both togethet'. There is also a treble bleed cap on the P pickup (not in the diagram) that, because of the VVT wiring, can also act as a 'really small' tone cap on the J pickup when the P is fully 'off'.
    Wiring Diagram.jpg
    * It is pseudo-passive bacause there is a JFET buffer after all of the usual gubbins which creates a low impedance output but has no real impact on the tone shaping beyond presenting a very high impedance load that preserves the full range and seems to add a degree of resonance when the tone control is backed right off. Yum!
  3. micguy


    May 17, 2011
    Thanks for a few more seconds of my “15 minutes of fame” - it’s nice to see someone grasp a relatively simple, but quite powerful concept that can have a dramatic impact on your tone.
  4. fermata

    fermata Guest

    Nov 10, 2015
    It really is a powerful concept -- so powerful that I imagine aftermarket pickup manufacturers may prefer for it not to be generally grasped. :greedy:

    One more thing I could have made clearer above: we're not talking about tone controls and their capacitors here. A loading capacitor plays a different function (as @micguy's second quoted post explains); loading caps are usually in the .001 - .005 uF range -- tiny, compared to the .022 - .1 uF caps normally found on tone controls.
  5. SteveCS


    Nov 19, 2014
    Hampshire, UK
    The bypass cap on mine is about 0.010uF, so is exactly this (the bolded part). To my ears it just takes the shine off, but perhaps I'm missing something. If you imagine it between the wiper and out (the two red lines) of the neck pickup pot - when neck is rolled off the cap ends up between hot and ground via the wiper.
  6. bdplaid

    bdplaid Supporting Member

    Aug 31, 2007
  7. Bassamatic

    Bassamatic keepin' the beat since the 60's

    Well, a cap from hot to ground is a tone roll-off cap. The smaller value just rolls off higher frequencies than the main tone cap, but all the time.

    I don't think that this is the same as Z-Mode.
    DJ Bebop and SteveCS like this.
  8. bdplaid

    bdplaid Supporting Member

    Aug 31, 2007
    If you're just talking about using different caps on the tone control, yes. the Z-Mode changes the resonant frequncy of te pickup. It's very cool. Definitely sounds like different pickups.
    DJ Bebop likes this.
  9. I was just going to say that :)

    I got one of those and it came with a bunch of disk caps to try.
    bdplaid likes this.
  10. superheavyfunk


    Mar 11, 2013
    Is all this very much different than what a tonestyler does, or just attaching a bunch of different capacitors to a rotary switch and selecting the one you want that way?
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  11. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion

    Aug 25, 2010
    The Great Midwest
    Very cool info I have got to learn how to solder
  12. StayLow


    Mar 14, 2008
    This rules.

    Oh, the money & soldering & time we could’ve saved.

  13. 40Hz

    40Hz Supporting Member

    May 24, 2006
    Great post!

    You can also insert a small value fixed or variable resistor in series with your pickup between the hot lead and pot to alter the resonances in your LCR circuit. Helmuth Lemme discusses this and other considerations in his classic book - Electric Guitar: Sound Secrets and Technology 2nd Edition. :thumbsup:
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  14. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    Yes, it definitely works. I have a six position rotary switch in my P-bass with one open position and five different caps on the other five positions. There is no variable resistance of a pot or other device that adds resistance, just a cap between the pickup signal and ground. Works great. I get a unique mid bump to my tone on a couple of the caps.
  15. Freekmagnet

    Freekmagnet Commercial User

    I built a little DIY Tone Styler and stuck in a bass once. It was pretty cool! There was definitely one or two caps I really preferred over the others. I suppose which caps I like would vary with different pickups. I thought the rotary switch was a little fiddly for a bass, but I could see finding a couple of choice caps and using a two position switch instead. Or maybe put a 16 position switch into a stompbox - that would be cool.

    I used an expensive Grayhill switch, and the whole unit was a PITA to build. If I was going to do it again, I think I'd just buy the Stellar ToneStyler.
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  16. coy garcia

    coy garcia

    Jan 18, 2020
    Instead of a tone pot I prefer a switch to go between 2 different for playing, one for soloing. One bass is like this and others are being changed over.
    StayLow likes this.
  17. superheavyfunk


    Mar 11, 2013
    This was a legitimate question, for those of you that might know the answer. I have a tonestyler kicking around and thinking about giving it a try
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  18. I think it is different but I could and can be wrong.

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  19. GreatRandini


    Jan 7, 2022
    love this post!
    DJ Bebop likes this.
  20. rufus.K


    Oct 18, 2015
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