How Can I Improve The Taper Of A Tone Pot?

[hardys]

I have a PRS McCarty that has a lousy tone pot taper. From 10 to 4, only minor changes occur, with just a slight roll off of the highs. From 4 to 0, the roll off is extreme and difficult to dial in without severe changes in tone. It's sort of all or nothing, with no smooth graduation in sound. I'd really like to have the taper evened out through the entire range.

This is a mini push/pull pot and I've read these generally have a poorer taper than full sized ones. I've also read that the taper can be changed using different capacitors. Currently there is a factory ceramic, .022 cap installed. Before I go in there and perform surgery, I was trying to get some opinions on what the culprit might be. Pot, cap, or both? If it is the pot, I read somewhere that Bourn mini push/pull pots have a better taper than other minis.

Any advice on this would be greatly appreciated.

[Jef Bardsley]

It's the pot, not the cap.

You can change the slope of the taper of a pot by adding a resistor across it, but you can't really fix a pot with a sharp knee. I'd change the pot.

[walterw]

is the pot an audio or a linear taper?

that sounds like what linear tone pots do, which is pretty much nothing until they're almost all the way off.

the pot should say on it somewhere either "500kA" or "500kB". "B" means linear taper.

this is odd, as PRSi usually have very nicely-tuned circuits.

[hardys]

It's the pot, not the cap.

You can change the slope of the taper of a pot by adding a resistor across it, but you can't really fix a pot with a sharp knee. I'd change the pot.

From what I've found so far, there are only a few manufactures of mini push pull pots. Any recommendations for one with a better taper? As far as change the slope of the taper, what value(s) of resistors are a good starting point. Also, how/where is the resistor installed? On the pot lugs?

[hardys]

is the pot an audio or a linear taper?

that sounds like what linear tone pots do, which is pretty much nothing until they're almost all the way off.

the pot should say on it somewhere either "500kA" or "500kB". "B" means linear taper.

this is odd, as PRSi usually have very nicely-tuned circuits.

Thanks for the tip. I need to check if the pot is audio or linear taper.

[Jef Bardsley]

Bourns and Alps make good high end pots, but from the pictures, they're sourcing their mini push/pulls from the same place in China. It may just be the specific pot you have is bad.

You could make the taper "steeper" by adding a resistor (same value as the pot) across the two lugs that are used, but this will halve the value of the pot. That is, to make a high taper 500K pot, I'd start with a 1 Meg pot. (Which is why I suggested simply changing the pot out)


Tone controls are a weird circuit..... maybe what you want is simply a lower value pot. Do you actually use the coil split? (I think you can see where I'm going with that question....)

[hardys]

Bourns and Alps make good high end pots, but from the pictures, they're sourcing their mini push/pulls from the same place in China. It may just be the specific pot you have is bad.

You could make the taper "steeper" by adding a resistor (same value as the pot) across the two lugs that are used, but this will halve the value of the pot. That is, to make a high taper 500K pot, I'd start with a 1 Meg pot. (Which is why I suggested simply changing the pot out)


Tone controls are a weird circuit..... maybe what you want is simply a lower value pot. Do you actually use the coil split? (I think you can see where I'm going with that question....)

Thanks for the help. Do I actually use spilt coils? Good question! I haven't started gigging with this guitar yet, so I'm not sure how splitting coils and having that volume drop is going to work in a live situation. If I end up not liking in, I may just put a full size pot in there and be done with it. It's kind of sad how the quality of some things like pots, etc. keep getting worse instead of better.