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Pots questions

Discussion in 'Pickups & Electronics [BG]' started by McCalister999, Aug 8, 2005.


  1. I know this sounds newb-ish, but I've been wondering for a while, what are the different kinds of pots and the numbers associated with them? I see a lot of 250k on these pots, but I have no idea what they mean. Can anyone fill me in on this?
     
  2. utopia_imminent

    utopia_imminent

    Jun 19, 2004
    the resistance of the pot. 250k means that the pot has 250k ohms of resistance. if you turn the knob of the pot, what you are actually doing is increasing and decreasing the resistance. the lesser the resistance, the more current flows through. thus, the larger the volume or tone.

    hope this helps
     
  3. Usually the volume pots are wired up to go from no output to 100% output , regardless if they're 250k or 500k, whatever. The value is chosen to match the impedance of the pickups.

    Randy
     
  4. what about on pots for treble and the like? Is it the same principle?
     
  5. Probably not, they generally are hooked up as variable resistance with a capacitor to roll off treble. Talking about passive controls, obviously. I'd have to look at the schematic to be sure.

    The value of the volume pots is relatively optional, doesn't affect the outcome within reason. The tone pots have to be specific values to go with the capacitors chosen for the circuit. They're effectively a matched set. If you change the pot value, you'll have to change the capacitor to match if you want to maintain the same effect.

    Randy
     
  6. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    Memphis
    Randy,

    Not to be confrontational, but that's just not the case. There are only two factors when it comes to tone pots: the resistance (how much of a load will the pickups see when the volume pots and tone pots are all in series) and the taper (linear or audio[logarhythmic]). Then you choose the tone circuit capacitor based on how dark and what kind of midrange emphasis you want.

    If you change out the tone pot, you don't have to change out the tone cap.
     
  7. woah, now I'm totally confused, does anyone know a website where this is all explaned? :confused:
     
  8. Not to be non-confrontational, but I don't disagree with you. ;) I'm reading his question as "What's the difference between 250k and 500k pots for tone control?" as in can you substitue one for the other.

    What part of my statement do you disagree with? You can substitute pretty much any higher value pot for a volume control with minimal or no tone change, you can't necessarily go with a lower pot since that may load the higher impedance pickups.

    Not so with the tone pots, they need to be the same value as the old ones to avoid drastic changes in tone.

    I guess I'm assuming the goal is a specific tone, I said the tone pots and the cap are a matched set, neither can be changed without affecting the resultant tone. You have some ability to compensate somewhat for a smaller pot by substituting a smaller cap (and vice versa), try to minimize the changes, but that will still not get you exactly the same tone, or range of tone control that you get with the original pot.

    So I'm saying there's much more flexibility in pot values for volume pots, there's a minimum to avoid loading the pickups, anything over that should work fine. But the tone pots are a matched set to the caps selected, you can't change either of them without significant changes in tone and range of tone control provided by the tone knob.

    The only conflict I see between us is I was assuming he was asking about the difference between pots as far as replacing one and maintaining the existing tone, and you are maybe assuming he's asking from the perspective of picking one when building a guitar from scratch or where you specifically DO want to change the tone?

    Other than that perspective, I don't see a conflict between our statements....

    Randy
     
  9. Also, to elaborate the K stands for 1,000 so a 250K pot's resistance is 250,000 ohms. There is also usually a suffix of 'A' or 'B'. 'A' indicating 'audio (or logarithmic) taper - typically used for volume controls and 'B' indicating 'linear taper - typically used for tone controls.

    Here's a link with somne information. Also, just Google for potentiometers. http://sound.westhost.com/pots.htm
     
  10. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    Memphis
    We'll start right there. You can't go to a higher value pot for volume with minimal tone change. The tone will get increasingly brighter, to the point where it will be unpleasantly bright if you go up to a 1M pot.

    They aren't "matched sets". You can keep the same cap and pot type (audio or linear) and change out the value and get a slight tonal difference when the pot is on 10, but it will sound about the same once you roll the tone off.

    You make it sound like "oh, you want a 250K tone pot and a .047uf cap, but if you want to use a .022uf cap you'll need to get a 500K tone pot."

    But that's false. The impedence of the pot, the value of the cap, and the taper of the pot all come together, but none of them are "matched sets".

     
  11. He's not saying that you have to have a 250k pot with this cap, and a 500k pot with this cap. He's saying that if you want the same tone as you had before, you're going to have to use the same value pot and cap.