Do better pots mean better tone?

[harryjmic]

I got a question for all you hard core techies out there. I know a bit about electronics and have heard that once the volume is all the way up on a guitar there is no resistance and this why you get a bit brighter tone when the volume is on 10. The pot is a variable resistor and as you turn it down you add resistance to the signal thereby changing the tone.

My question is this: Does some of this brightness have to do with the quality of the potentometer used or will all pots work the same? I would like for the pots in my guitar to not have such a drastic jump in treble when I turn the volume from 8 to 10.

[John Phillips]

The reason for the treble loss is more complicated than just resistance, and is due to the interaction between the pot and the cable.

Basically you have an AC potential divider between an inductive source (the pickup) and a capactive load (the cable) - but if that sounds like Chinese to you I won't go any further or it will make your head hurt :).

The pot value (usually 250K or 500K ohms) affects the brightness at 10 (higher = brighter) and also the proportion of treble loss as you turn down (higher = more loss).

The pot quality does also make a noticeable difference - physically bigger pots (US-made CTS, or similar) have a bigger, more open and brighter tone than smaller ones (eg typical Far-East made mini-pots). This is due to the 'parasitic' capacitance of the parts and materials in the pot.

BUT - more important than either is the cable, which affects both the brightness at 10 (somewhat) and the rate of treble loss as you turn down (a lot). If you want to see this really clearly, sit right on top of the amp and plug in with the shortest cable you can get - like a 6" patch cord. Of course you can't do that normally, but any shorter and higher-quality cable than the one you're using will help.

You can also add a small 'bypass' capacitor to the volume control - some guitars come with these fitted as stock, most don't. It goes between the two non-grounded tags on the volume pot, and allows more treble to get through when the pot is turned down. The precise value depends on your preference, pickups, and cable. Some people like a resistor in series or parallel with the cap too, to moderate its effect.

[Clorenzo]

If you want to see graphically the effect of different pot values, cable capacitance, etc. described by John, check out my volume and tone circuit simulation spreadsheet here:

www.harryj.net/voltone.xls

[doublestop]

FWIW: I have done some experiments on a 335-style guitar. I used various pots and caps. Various types and brands. The value did have an influence on the tone, but the quality.......hardly, if any. At least MY ears don't hear it.

[Old Tele man]

this post reminds me of a similar automotive addage:

Q: Will better tires make my car quicker?
A: ...not if it's now sitting on blocks.

[KLB]

IMO, treble bypass caps on volume controls -- whether in the guitar or amp -- usually make the inital attack too exaggerated compared to the body of the note. This can lend a "plinky" quality to the tone, especially on high notes.

I'd rather set the amp brighter and rolloff the treble on the guitar.
Then when lowering the volume, if I wanti more treble, I can turn up the treble using the guitar tone knob. This also lets me create a more sparkly "quack" tone if desired.

YMMV.

[malabarmusic]

Originally posted by KLB
IMO, treble bypass caps on volume controls -- whether in the guitar or amp -- usually make the inital attack too exaggerated compared to the body of the note. This can lend a "plinky" quality to the tone, especially on high notes. Hmm, this makes me wonder whether my impression of Tom Anderson guitars as thinner sounding than other similar designs.

- DB

[Jim Collins]

Originally posted by KLB
I'd rather set the amp brighter and rolloff the treble on the guitar. Then when lowering the volume, if I want more treble, I can turn up the treble using the guitar tone knob. This also lets me create a more sparkly "quack" tone if desired.


This is exactly what I do. I set the amp up to be brighter and louder than I'll need it. For me, the sweet spot on a guitar is usually with the tone control rolled off, a bit, and the volume somewhere less than full.

[Dave Paetow]

There is a definite tonal difference between pot brands. You can easily hear the difference between the commonly used CGE pots and the CTS pots. CGE's are more muffled sounding and seem to dampen the harmonics somewhat, and CTS has a brighter high end and more clear sounding. There also is a wide tolerance to the pots, just because it says 500k on the pot doesn't mean it reads 500k. I've seen CTS 500k pots range from the lower 400's up to around 560k. Sometimes I use the lower reading ones for bright guitars, and the higher ones for darker guitars.