1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Passive Tone Circuit Capacitors

Discussion in 'Pickups & Electronics [BG]' started by extrastout99, Dec 16, 2017.


  1. I'm currently building a passive pre-amp circuit for my fretless Fender Jazz. I've already upgraded the pickups to a set of Norstrand NP4 P/Js. The controls will have a master volume, pickup blend control, and tone control. The pre-amp I'm replacing had a varitone that allowed me to choose the value of the capacitor in the tone circuit. I would like to install a toggle switch to choose between the .047 mfd cap and another value cap. Any suggestions out there for what value I should choose for the second cap?
     
  2. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    Do you want the second cap to give you a darker or less dark tone range?
     
  3. You should be experimenting to let your ears decide what is useful. Actually, since you used to have a varitone, you should already know which capacitance was your favorite.
     
    lz4005 and Haroldo like this.
  4. fermata

    fermata

    Nov 10, 2015
    Mountain West
    You have lots of options, and what sounds good depends on several factors, including your ears and the pickup(s) on the bass: .022 uF can be cool; it lets through a lot of mids but can also get a bit honky, depending on the pickups. .03 uF is very nice, but perhaps not dramatically different enough from .047 uF. .068 uF and .01 uF get you into the dub realm. Then there are low value caps, like .01 uF, .0068 uF, and .0047 uF, which can yield some interesting, sort of woody sounds (or, alternatively, very subtle sounds that aren't worth it). All to say, it's worth running a couple of alligator clips out from the control cavity so you can experiment with a few different values. (And don't spend big money on caps--any cheap cap is fine; the only ones I'm not a big fan of are some ceramics that have a +/- 80% tolerance, because unless you can test them, you don't really know what the actual value is. But if you have a handful of them, then it doesn't matter--just pick the one you like the sound of.)
     
    extrastout99 and Haroldo like this.
  5. Haroldo

    Haroldo Supporting Member

    Aug 31, 2005
    North Shore, MA
    Always do the experiment (but use care).
     
  6. Having a switch is kind of superfluous when you have a knob to make the adjustment.
    Just put in the largest value of cap you're comfortable with (along with a 500k Ohm pot) & then you'll have all the range for adjustment that you need.
     
  7. fermata

    fermata

    Nov 10, 2015
    Mountain West
    Two cap values (even attached to a rheostat) won't sound the same, since the hinge frequencies (and related resonant bumps) are different. Whether or not one finds multiple hinge frequencies useful is another question.

    And yet another question--why the 500K pot? To my ear, 250K is more useful, since the effect of the capacitor kicks in sooner, allowing more variation across the sweep. 500K seems to bunch up the more noticeable effect toward the end of the pot's travel. Just curious.
     
  8. They won't sound the same with a 250K Ohm pot, which is why I recommend a 500K Ohm pot.
    A 250K Ohm pot is giving the cap more effect on the overall timbre (damping the highs), even before you roll it back.

    Dialling back the pot on a wider range just seems better to me than having a switch.
     
    Last edited: Dec 18, 2017
    40Hz likes this.

Share This Page