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Capacitor

Discussion in 'Pickups & Electronics [BG]' started by Sippy, Sep 7, 2005.


  1. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    Hey guys, im picking up some capacitors for my fender, and just wanted to make sure i'm getting the right ones. I want it to be a bit deeper, yet not lose all the highs. So I'm looking at .020mg or .050mg.. stewmac also has .001 but that has to be way too low. Thanks a lot guys :)

    Mike :ninja:
     
  2. Capacitors only roll off the highs. They don't boost bass. The larger the capacitor the more highs are rolled off as you engage the tone knob.
     
  3. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    I'm sorry for such a noob question, hehe but what is meant when somebody said "highs are rolled off" I searched before I posted this and I really didn't understand that.
    This is what happened, I just recently replaced my pots. The Fender pot came with a capacitor and like an idiot I used that one without looking at it's specs. Well the tone of my bass his a decent amount higher then the tone of other MIA Fender P-Bass' thats when I realized that capacitor was probably meant for a guitar. Therefore would naturally be higher than a bass. So I'm assuming when i change the capacitor it should help out a bit.
     
  4. When you turn the pot to the end point where you get the brightest sound you're essentially hearing the full sound of the pickup(s). As you turn the pot from that position you start to eliminate the highest frequencies. The more you turn the pot the more treble frequencies are eliminated. It starts with the highest frequencies and works its way down.

    A capacitor meant for a bass will eliminate more of the high frequencies than one meant for guitar.
     
  5. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    Yes, so wouldn't that make the sound deeper with a capacitor meant for a bass? I'm probably not understanding 100%.. the way that i'm thinking of how it works is; just say for arguments sake the capacitor in my bass right now is meant for a guitar and is .100mg it probably isn't, but just for arguments sake. Now if I took that out, and put in a .001mg, the way that I understand it, is that will give my bass more of a "bass" sound. A darker, deeper, lower tone. Rather than a higher, more trebely tone.
    Am I wrong?

    Mike
     
  6. Wademeister63

    Wademeister63

    Aug 30, 2004
    Denton Tx
    Think of a capacitor as sort of a shock absorber for electronics. The larger value, the more damping you get. So the bigger cap will kill the higher (faster moving) frequencies. You will hear less treble, not really more bass. The pot just blends the straight signal with the filtered signal.
     
  7. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    Awesome! that helps a lot! now the only question I have is kinda hard to explain. Does it kill the treble through the whole tone range? or just at the top? For example. I have my tone knob set at the lowest setting, will it get rid of some treble there too? or just at the top of the tone range?
     
  8. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    TBer DavePlaysBass did this simulation of a JB network with 250k pots and a 47nF (0.047) tone cap, ie a fairly typical passive tone control network.

    http://www.talkbass.com/photopost/showphoto.php?photo=1929&size=big&password=0&sort=1&cat=500

    Look at the magenta curve: that's with the tone pot fully open. Now look at the green one: that's with the tone control fully closed. As both curves begin to drop as they move to the right, any frequencies above this point are attenuated, or reduced. So as you 'close' the tone control, the more upper harmonics are reduced and the frequency where that reduction starts gets lower as the pot turns more counterclockwise.

    If you use a larger cap, both curves will be shifted to the left, a smaller cap, to the right.
     
  9. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    I'm colorblind man :( hehe damn.. I think I understand the graph tho! :) thanks!
     
  10. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    Magenta = 250k and green = 0-ohm
     
  11. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    unfortunately, shades of red and green are generally the first to be confused when someone is (genetically) color-blind...
     
  12. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    what value and position volume pots does this graph require?

    my gut says (2) 250k's in parallel (with rotation up fully) based on the frequency cutoff indicated by the "0 ohm" line...
     
  13. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    I didn't do the original simulation and diagram, but it makes sense that it uses the tradition series variable resistor pot, fully open.
     
  14. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    Yea I forget what it's called but I've got a rare form of colorblindness, I can't distinguish ANY colors.. I can see colors, I just don' tknow what they are :(
    Anyway I just checked on my bass, it is a .1k capacitor, and I just ordered .050k caps from stewmac.. this should make my bass sound more like a bass ;)
     
  15. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    except that the pots aren't wired as variable resistors, nor are they in series...

    i just pulled up a wiring diagram- the pots are in parallel, for starters, and they're wired as voltage dividers...

    why is any of this important? this means that the corner frequency in those charts is going to change as you change volume settings...

    regardless- it's still a good chart that shows the general trends- but the actual info in it is pretty much useless...
     
  16. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    At 2am, I sometimes don't read diagrams correctly especially the hand drawn one I have. I just double checked the one on the SDuncan site. FWIW, I don't normally have anything to do with passive instruments, unless it's to do a repair so they're not the first things I think of.

    And by "in series", I meant in series with the pickup output, not two volume controls in series. Note that at any setting apart from fully on at least part of the pot's resistance is in series with the output of the pickup. See below.
    Not quite. The pots aren't wired as traditional voltage dividers.

    http://web.mit.edu/rec/www/workshop/voltage-divider.gif

    The way the JB has the pots wired has in Vin and Vout reversed. Looking at just one pickup and pot; fully on, the pot is a 250k resistor in parallel with the pickup. Fully closed, the pickup is shorted and the pot's resistance is in parallel with the combination of pickup 2's network and the tone pot/cap series element. At any other setting, part of the pot's resistance will be loading the pickup to ground, and part will be in series with the node that consists of the second volume pot and the tone pot wiper.
    It's a passive bass, so of course it's reasonable to expect a whole lot of passive elements in a network are going to interact, unless you have an active buffering element in between them.
    It was only ever intended to show a trend, which it does well and clearly. Specific analysis of a network with three variable pots and three reactances (four including cable capacitances) that show all possible variations of each element is going to make an unwieldy chart that's going to be very difficult to interpret for the average non technical person.
     
  17. Unfortunately, a .050 cap will roll off LESS treble than a .100 because the .050 is a SMALLER value cap (decimal places). You might want to try something larger like a .22. A cap of .1 is a capacitor used in basses and will roll off more treble than the stock Fender cap.

    Save yourself a bunch of money and find the value cap you're interested in and then note the image of the cap on some site like Stew-Mac and then go to Radio Shack. There are different types of capacitors so find one that looks like the images on Stew-Mac.

    At Radio Shack you can buy them in ones or twos without the shipping charge and you can experiment for a fraction of the price of shipping a single capacitor.

    Or if you really want to eliminate the treble just turn down the treble control on your amp. It will eliminate more treble than any typical on-board capacitor. The treble control on your amp does the same thing only to a greater degree.
     
  18. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    woah- i looked closer, yes, jbass volume pots are wired strangely... i wonder why?

    as for the series/parallel thing... it doesn't matter how it's wired with respect to the pickup... gotta look at it from the cap's POV. (er, not that it's a person, but you know what i mean).

    did you actually simulate this in pspice? or just plot what the lines would based on simple calculations?

    still- this graph is pretty cool. :)
     
  19. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    If you had the two pots wired as trad voltage dividers, and you had one of the pots closed, the other pickup would be shorted.
    Not quite sure what you mean, but tall the elements of the network are interactive.
    No, another TBer, DavePlaysBass simulated it and I merely borrowed it to illustrate a point as this is the first drawing of it's type showing the effects of tone control elements in basses that I've seen (now I've said that, somone will pipe up with others). It was done in some sort of sim program I beleive, but I dunno what. I was going to draw it up by hand, but the graph is neater, and since I moved away from electronics full time (I'm an EE) I don't have access to Spice at home to do them myself.

    A pic makes it so much easier to explain things like the shape of curves.
     
  20. Sippy

    Sippy

    Aug 1, 2005
    Stuart,Florida
    oh well.. too late now I already placed my order. I wonder why my bass sounds so high. To those of you with vintage Fenders, does your sound higher in tone, then a brand new fender?