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Capacitor Options

Discussion in 'Luthier's Corner' started by Crash Course, Aug 24, 2005.


  1. I Know capacitors have been talked about in other posts, but none have come to this question. I understand that the Larger the capacitor is the more treble it rolls off. I also know that the P and J use .047. My question is would a .1 be to much and make it sound muddy. By the way my wood selection is mahogany body, Padouk neck and Pau Ferro fingerboard.
     
  2. tjclem

    tjclem Supporting Member Commercial User

    Jun 6, 2004
    Central Florida
    Owner and builder Clementbass
    I use .1 in most of mine. to me it just gives you more range. Each to his own try it. .....t
     
  3. RyanHelms

    RyanHelms

    Sep 20, 2003
    Cleveland, OH
    CC, I played a bass once with a push/pull knob that selected between .047uf and 0.1uf tone caps. With the tone rolled back & the 0.1uf selected, there almost seemed be a bass *boost*. Of course there wasn't, but that's a clue as to how much relative difference there can be.

    Pickups and pot values are also as responsible for your tone as your wood selection. Let's say you use very dark PU's to begin with, and 250k pots - you may want to go with the smaller tone cap since there's going to be less treble content to begin with. Unless you *want* to be able dial all the down to deep dub, that is ;)

    OTOH, if your PU's are bright & you use 500k or 1M pots there's going to be more native treble content. Then a larger tone cap will let you dial down more of that. See what I mean?
     
  4. Thanks alot Ryan! that is some of the best info I have gotten from talk bass in a long time. You even answered the question I had not asked yet (Pot value differences).
    Thanks a million. :hyper: :)
     
  5. dpmasunder

    dpmasunder

    Apr 30, 2005
    'Straylya
    Tone caps work by shifting the resonant peak of the pickup lower, so shifting it low enough will give a bass boost effect.
    Note that the frequncy response of a pickup rolls off above it's resonant peak, which is why we interpret tone pots as treble cut.
    I found a good explanation of all this once, I'll look for it again if anyone wants.
     
  6. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    I've never understood how pot values are supposed to affect treble response. How much resistance they have at one end of the dial should have no bearing on their response in the full open position where they all have minimal resistence. I tend to think this is a bit of a myth.

    In a simple tone circuit changing a caps value moves the frequency roll off point and the math is rather simple. Double the cap and you move the point one octave down. Going from .047 to .1 is just a hair over double so the .1 will also remove the high end but will cut one octave deeper than the .047. Conversely if you went to a cap of about .024 the treble rolloff would start one octave higher.

    Also a passive tone pot does not change the resonant frequency of the pickup, it is a simple low pass filter and actually does cut treble out of the signal.
     
  7. dpmasunder

    dpmasunder

    Apr 30, 2005
    'Straylya
    Yes, the tone pot does cut treble, but it goes hand in hand with the resonant freq. lowering.
    I'd agree that pot values theoretically shouldn't affect the signal when on full open, but they always have a small amount of capacitance*. I wouldn't believe it myself if I hadn't tried it. Take it to the extreme, put a 25k or 50k pot on a passive pickup and see what happens.
    Refer here for inductance and capacitance info http://www.buildyourguitar.com/resources/lemme/

    * This is incorrect re. vol pots, the issue is not capacitance but load.
     
  8. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    It doesn't change the resonant frequency of the pickup when used in a low pass filter.

    Resistance are capacitance are easily measured. What is the capacitance difference between a 500k and a 25k pot when fully closed?
     
  9. dpmasunder

    dpmasunder

    Apr 30, 2005
    'Straylya
  10. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    Leo Fender says a whammy bar is a tremelo. ;)

    Advertisers will often say crazy things and the internet doesn't mean something is true. If it did you would accept what I wrote. Do you believe what's on the Tara labs site?

    "Higher value pots and capacitors cause the pickups to resonate at a higher frequency and develop more output and presence with the result that the sound is noticeably brighter."

    I thought you said a higher value cap would lower the frequency ;)

    I have a friend who loves Kinman pickups but don't go to him for a science lesson. He's talking about a pickup resonating and pots making pickups louder, he's absolutely clueless!
     
  11. dpmasunder

    dpmasunder

    Apr 30, 2005
    'Straylya
    I have a few corrections and comments re. your last post.

    Leo Fender doesn't say anything. He's dead.
    I'm not aware of his use of the term 'whammy bar'.
    It's tremolo, not tremelo.
    He did reverse the terms vibrato and tremolo.

    Your thought was incorrect. I did not make any statements regarding cap values.

    I'm not a huge fan of Kinman's pickups, but this is a bit harsh. I do admit that particular Kinman quote is poorly written.

    I've never seen it, can you provide a link please?

    I can also tell you DiMarzio recommend 1M tone pots for their original Virtual Vintage pickups - to give better high frequency response. EMG recommend 50k pots instead of 25k for their bass pickup - to give better high frequency response.
    Why would these people lie? What have they got to gain by recommending something that, according to you, doesn't alter tone? How many references do you need? I can email pickup makers directly if you like.

    Moo, what makes you the expert?
    I'm not trying to start a war here, but you have presented nothing to prove me wrong. :)
    I work full time building, repairing and modifying guitars, and have been doing so for a long time. I know pot values alter tone, because I have experimented with them. I believe caps alter resonant peaks because I have read very good explanations of it, I have read it from several different sources, and I can hear the result.
     
  12. Tim__x

    Tim__x

    Aug 13, 2002
    Alberta, Canada
    Pot values do have a significant effect on the Q of the pickups resonance


    The pot itself doesn't, but the tone control has a whole does. You're changing the value of C in a series LC resonator.
     
  13. Tim__x

    Tim__x

    Aug 13, 2002
    Alberta, Canada
    Attached is a sim of a guesstimate pickup.
    Red is 500k
    Blue is 250k
    Green is 100k.
     

    Attached Files:

  14. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    Dave do you even know what a potentiometer is? It's resistance value is irrelevant in the off position. Do you have a DMM? I can walk you through a simple experiment to help you understand what a pot does.

    I see you're more interested in just arguing. Enjoy the internet.
     
  15. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    Do they change how a "pickup resonates"? That's the bad science I'm dealing with here.

    And in the full volume position what is it about a pots value that will affect tone? Please tell me something that can be measured and compared to another pot of a different value.

    Instead of simply just saying they do there must be something that can be tested and measured. So what can I detect between the 2 different pots at full volume that would affect tone? Surely if it will change tone audibly it can be measured with sensitive instruments.
     
  16. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    Do you understand that for a 500k pot to have a resistance of 500k ohms it must be in the off position? In the on position it is close to 0. Your chart is a guess of the frequency responses of pickups in the off position. This is like comparing amps unplugged, not really useful.
     
  17. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    So has Wish basses ;)

    This kind of argument is rather petty but since you're beating your chest I've been working with guitar electronics for over 20 years and have designed and built pedals from scratch. Here is one example of a bass where I have designed and installed a circuit, and built the entire bass from raw unsurfaced lumber up, please show me an example of your work now that you have made this ridiculous challenge.

    http://photobucket.com/albums/v484/alphonsopuppetshow/basses/?action=view&current=FretlessBody.jpg

    If you don't show me something more impressive I'll have to assume you are ignorant in this area based on your silly challenge.

    You simply are confused with what a pot is. It's rated value is the maximum resistance that can be achieved, not it's constant load. What good is a variable resistor with a fixed resistance?

    But let's not get lost in your internet posturing, tell me what I can measure between 2 pots of varying value in the full on position that will affect tone? Tell me what a potentiometer does.

    Or just look for more spelling mistakes :rolleyes:
     
  18. Tim__x

    Tim__x

    Aug 13, 2002
    Alberta, Canada
    I showed you in the second post, at full volume and with the tone control off (on it's minimum setting) lower value pots lower the Q of the pickups resonance.
    It does change the resonating frequency as well, like I said, it's a series LC and the tone control allows you to parallel another C with the first (parisitic) C, thereby changing the value of the C in LC, and its resonating frequency.


    The value of the volume pot matters at all settings, the value of the tone pot matters only when it is a set higher than the other value of pot in question.
    My graph shows the response of a bass with a single pickup with an approximately 5k resonance with the volume on full and the tone control "off", those are the setting I use most with a P-Bass. It is not like comparing amps unplugged.
     
  19. dpmasunder

    dpmasunder

    Apr 30, 2005
    'Straylya
    Thanks Tim. As most people are aware, very few pots are capable of being completely out of circuit.
    My name is Dan, btw.
    A guitar pickup is a coil, a coil is an inductor, capacitors are used to tune the resonance of inductors in all sorts of circuits.
    This is getting lame, but since you ask.

    [​IMG]
    [​IMG]
    [​IMG]
     
  20. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    Ok, forgive me if I'm wrong, but isn't a basic passive guitar circuit an RLC (as opposed to RC) circuit - so the R matters? (Or, more exactly, "the Rs matter"?)

    Specifically, with a tone control, even when it is turned to "least treble rolloff effect," that tone pot is a resistance in series with the cap, and, as such, is still allowing some amount of treble to be shorted to ground through the cap. The amount of high frequency signal that follows this path to ground is determined by the ratio of this (tone pot) resistance to the other parallel paths to ground - namely, the volume pot and the amp input resistance.

    This is because, since this is a circuit, all the signal, both treble and bass, eventually find their way to ground. There are simply three paths that the signal can go through (that is, beyond the pup itself), to varying degrees depending on the frequency. The more of it that gets by the tone and volume controls, the more will be amplified (by the third path, the amp input).

    Right?

    BTW, I re-checked the basic theory here before I posted.