Tone Pot Range

thegummy

If the tone control on a guitar basically does nothing from 10 down to about 7 but then from 6 down to 0 it tapers off the tone gradually, what change can be made to make the usable range span more of the knob's rotation?

I'm fairly sure it's a 500K pot but can't remember if it's audio or linear and can't remember what cap it has on it.

Thanks guys.

CasperCaster

With a log pot I would expect quite a lot of change between 10 and 7, so I'm going to guess that's a linear pot? 

The cap sets the corner frequency of the tone control. Small value for treble, larger value for treble and high mids.

Tolerance/ accuracy of pots is described as a percentage. The steepness of the log curve of a log pot is also expressed as a percentage - be careful you know which detail you are looking at. 

Lots of euphemistic terms in guitar cicles for the different %log tapers. I recall that either @gavin_axecaster or @sixstringsupplies once described who sold what versus actual %tapers but can't find the comment just now. 

So, log pots come with different curves, typically between a 10% taper for a modern pot up to 30% taper. A linear pot is at 50% resistance at 50% rotation and reaches that via a predictable straight line (give or take), eg 250K for a 500K pot. By comparison a 10% log pot would be at 10% of its resistance at 50% rotation, achieved via a curve, eg 50K for a 500K pot. Clearly a 10% log pot rolls off treble very much more quickly than a linear pot. And a 30% taper pot would sit between 10% log and linear.

If you don't like the mud in the lower reaches of the pots range a fixed resistor in the path to earth will effectively ensure the pot can't get to 0K. For example, if you never use the tone pot below '3' (on a knob scaled 1-10), and '3' represented 5K resistance, then a 5K fixed resistor means your tone pot is now at '3' even when turned fully down - you've now got greater resolution of control for the tones you actually use as the '10' down to '3' range has been extended '10' down to '1'. The 5K resistance will have negligible effect at '10' as its such a small percentage greater relative to the 500K of resistance of the pot. This trick is part of Fenders grease bucket circuit, which I mostly don't like, but the fixed resistor aspect of that circuit (as described above) can be useful. 

ICBM

That sounds to me like an audio (A) taper - a linear (B taper) basically does nothing down to about 3. If it is an A, you could try to find a true 10% Log (D taper), although they’re fairly rare in guitar pot types. If it is actually a B, then an A should sort it.

Failing that, a 250K - if it’s currently a 500 - would possibly help, although the tone at 10 will then be slightly duller. I’m not actually a fan of having the tone pot value lower than the volume at all, to me it never sounds quite right.

Funkfingers

To which terminal is the signal connected? 

How cheap is the pot?

thegummy

Thanks a lot for the replies guys

CasperCaster said:

If you don't like the mud in the lower reaches of the pots range a fixed resistor in the path to earth will effectively ensure the pot can't get to 0K. For example, if you never use the tone pot below '3' (on a knob scaled 1-10), and '3' represented 5K resistance, then a 5K fixed resistor means your tone pot is now at '3' even when turned fully down - you've now got greater resolution of control for the tones you actually use as the '10' down to '3' range has been extended '10' down to '1'. The 5K resistance will have negligible effect at '10' as its such a small percentage greater relative to the 500K of resistance of the pot. This trick is part of Fenders grease bucket circuit, which I mostly don't like, but the fixed resistor aspect of that circuit (as described above) can be useful. 

Brilliant advice cheers. Having the tone at 0 for a very muddy sound is actually a sound I do like sometimes though so hopefully there's another way to improve the higher end of the rotation.

ICBM said:

That sounds to me like an audio (A) taper - a linear (B taper) basically does nothing down to about 3. If it is an A, you could try to find a true 10% Log (D taper), although they’re fairly rare in guitar pot types. If it is actually a B, then an A should sort it.

Failing that, a 250K - if it’s currently a 500 - would possibly help, although the tone at 10 will then be slightly duller. I’m not actually a fan of having the tone pot value lower than the volume at all, to me it never sounds quite right.

I wish I could remember if it was audio or linear, I used to know everything about how I wired my guitars all up off by heart but after a serious medical incident I lost a bit of memory so now have to try and work it out from diagrams. Think I'll have to just open it up and check though, I think I remember that it says A or B on the actual pot. The 250k thing sounds interesting cause the pickups are fairly bright for humbuckers so having them slightly dulled at 10 might not be so terrible.

Funkfingers said:

To which terminal is the signal connected? 

How cheap is the pot?

It's a CTS one so not particularly cheap. It's the middle terminal that's connected to the volume pot's input. Does that have an effect on how it works I take it?

Dave_Mc

thegummy said:

I wish I could remember if it was audio or linear, I used to know everything about how I wired my guitars all up off by heart but after a serious medical incident I lost a bit of memory so now have to try and work it out from diagrams. Think I'll have to just open it up and check though, I think I remember that it says A or B on the actual pot. The 250k thing sounds interesting cause the pickups are fairly bright for humbuckers so having them slightly dulled at 10 might not be so terrible.

Wow, sorry to hear about that I don't even try to remember, I just have a file on the computer where I've written down everything I've done to the wiring... I change my mind so often I have to write it down!

Some (most?) of the pots say on the back what the value and taper are (though if you've soldered over that, that might not help!). Alphas say on the top as well (I don't think CTS does, but I could be wrong) but you have to take them out to see that.