Question on pot sizes...

[awfulguitarnois]

Hi,

I couldn't find an answer to this an am wondering: what dictates increasing pot size from 250k to 500k? Is it just the fact of going to hum/mini-hum, or is a factor of the pickup resistance?

Thanks!

[chisa]

higher value generally lets more treble through

[DMace]

Generally, 250K is used for single coils - because they're bright enough already, and 500K for humbuckers.

[chris klein]

It can be a matter of pickup resistance as well. Some times a Tele bridge pickup wound to 10k can use a 300k or 500k pot if it is too dark with a 250k.

General rule:
Single Coils 250k
Hums 500k

[chris klein]

One more thing to double check with POTS.

With them being 250k rated, double check them:

I have seen 250k pots when tested with a DC Ohm meter read, 225k-280k. They are with in a certain tolerance.

You can check them and if you have one that tests at 225k you could switch it to one that tests at 250k or 270k. It's tricky how this is.

[Parma_TeleMon]

Some Fenders came with 1M pots (like my '69 Thinline RI). After much experimentation, I've found that 250k volume and 1M tone works pretty well for me, even with a humbucker at the bridge. YMMV - it's all about your ears.

[surfoverb]

Originally Posted by chris klein

One more thing to double check with POTS.

With them being 250k rated, double check them:

I have seen 250k pots when tested with a DC Ohm meter read, 225k-280k. They are with in a certain tolerance.

You can check them and if you have one that tests at 225k you could switch it to one that tests at 250k or 270k. It's tricky how this is.

Ive checked several pots and they were all over the place, some 220, one 260, all CTS. I just ordered some Mojo designed CTS that hopefully will have a tighter tolerance than other CTS.

[gaddis]

Originally Posted by chris klein

...

I have seen 250k pots when tested with a DC Ohm meter read, 225k-280k. They are with in a certain tolerance.

You can check them and if you have one that tests at 225k you could switch it to one that tests at 250k or 270k. It's tricky how this is.

Not tricky at all. All electronic components have a tolerance. A tolerance of 10% is not unusual for a pot. Your 225K measurement indicates it was 10% lower than the nominal 250K value. Not unexpected and nothing to worry about really. For a pot used as a volume or tone control, the exact value is not very critical.

[charlie cash]

Not to highjack, but what is typically a good pot value for P90s? What would you typically try first?

[awfulguitarnois]

Thanks for all the great insight... this forum continues to be an amazing source of info.

[chris klein]

Originally Posted by gaddis

Not tricky at all. All electronic components have a tolerance. A tolerance of 10% is not unusual for a pot. Your 225K measurement indicates it was 10% lower than the nominal 250K value. Not unexpected and nothing to worry about really. For a pot used as a volume or tone control, the exact value is not very critical.

I understand there are tolerances that electronic parts are measured against. In a problem shooting of a dark sounding pickup or just wanting to brighten it up, a Volume pot with a measure of 225k would make a difference versus one that is 250k or 275k. One more variable that a less experienced person can use in a trouble shoot.

[JCollins]

Originally Posted by charlie cash

Not to highjack, but what is typically a good pot value for P90s? What would you typically try first?

Gibson originally used 500K for both volume and tone, for humbuckers and P90s. These days, Gibson uses 300K for volume pots, in their production (non-Historic) guitars. 500K pots with P90 pickups have always worked for me. If the guitar happened to be particularly bright, and a P90 pickup was mated with one or two Fender-style single coils, I might consider a 250K volume pot.