Tolerances, etc.

[Mini-Strat_Maine]

Okay, my turn for (another) question. (And there's at least one more after that.) How picky is everybody about tolerances on pots and other components?
In looking over some CTS data sheets (trying to find out which of their stock numbers correspond to the parts I need), I got the impression that audio pots were all 10% tolerance. I recently received a nominally 500K pot that reads 431K on my multimeter. Apparently there's a lot of 20% stuff out there. (See link below.)
I'm happier with the one I got from another supplier that measures 511K, because as John Spina says, "I always want the rated value of a pot or higher. If the pot reads high, I can knock it down some with a [parallel] resistor, but if it reads too low, I can't do much of anything with it." (www.projectguitar.com/tut/potm.htm)

So for a project on a humbucker-equipped guitar, how fussy would you be? And if you were willing to make use of the lower-value pot by putting it where it would make the least difference, would you make it a tone or volume control? (BTW, some of these [push/pulls] may get used with a parallel resistor to drop them to 300K or so in one position of the p/p anyway, so . . . )

Thanks for any input.

--
Doug C.

[JohnH]

I think the theory would say that if you were doing an A/B test between 430k and 500k pots in a guitar circuit, you would would be very hard-pressed to tell the difference. It is only a 16% difference in resistance. Going from 250k to 500k makes a slight difference, and that is why people consider one or other better, but that is a 100% or x 2 factor.

In sound perception, even x2 is only a small step. Used in this application however, the difference in treble level at minimum treble cut is much smaller

By a rough calc, assuming high inductance humbuckers, and looking at the high frequencies, I reckon the measurable difference in the highest treble would be about half of that 16%, ie, not enough to notice in a listening test

John.

[jimplaysguitar]

Yeah, what John said.
+1
;D

[Mini-Strat_Maine]

jimplaysguitar said:

Yeah, what John said.
+1
;D

Oh, okay, that whole logarithmic thing. I get it. Uh huh.
Thanks, guys.

[UnklMickey]

in a potentiometer, what is more important, is the quality of construction.

if your wiper has poor contact, any vibrations that disturb it, will cause horrendous noises.

a loose fitting bushing, or other sloppy assembly techniques just simply won't do.

you can usually tell the good stuff from the garbage by how it feels when you turn it.

if it feels firm and smooth, with no end-play or wobble, chances are, it will give years of quiet service.

[Mini-Strat_Maine]

unklmickey said:

in a potentiometer, what is more important, is the quality of construction.

you can usually tell the good stuff from the garbage by how it feels when you turn it.

if it feels firm and smooth, with no end-play or wobble, chances are, it will give years of quiet service.

And that's the downside of this Internet/mail order biz: ya can't test-drive stuff. The vendors that have (or at least say they do) CRL, CTS, Switchcraft, and other "known quantities" are the best bet, even if they're a little more pricey. I've learned to stay away from the Bargin Basement Electronics and Used Car Sales guys. "Guaranteed not to rust, bust, fumigate, rip, stink, or wrinkle for the life of your guitar! (Or until you're off our lot. Read the fine print.)"

Okay, I'm babbling again. Time for more coffee.