Volume Pot subbing

[dune2k]

Hi,
I forgot to order a volume pot (should be A100K), but I got a couple of 50K, 1M and I think also one 20K pot flying around here. Which one would be the best to use as a sub?

Project is this.

Cheers,
dune2k

[GibsonGM]

Try the 50k, it might give you good results.  I'd be happier seeing the 100k original, 250k, or 500k, tho.  It's all about output impedance and loading the next stage (plus filtering due to reactances with the 100n cap, and the input section of the next pedal, etc).  
The 100k was settled on because it gives you a good sweep over its range and will still keep output impedance low.  Try experimenting with all of them, see if you get any effects if going into another pedal (or your amp)!

[PRR]

> Try the 50k, it might give you good results.

Yeah.

In this _specific_ case:

The CMOS needs to see much-more than 300 ohms. This has some effect on distortion, and since the original used 100K I would not go a big-bunch lower like 1K or 5K.

The next box in the chain (another pedal or the amp) "might" want to see some impedance. Most "good" inputs are happy with very low impedance; however several pedal-circuits depend on the highish impedance of a pickup or something similar. That's maybe another reason to be higher than 1K or 5K.

The 100nFd cap, pot, and external load set a low-cut. If we assume the next-box is 100K, and 100K pot, set full-up, the 100nFd = 0.1uFd into 100K||100K= 50K gives 34Hz. Plenty good enough for guitar. A 1K pot would give 1.6KHz, cutting-off nearly all the guitar's ballz so it shrieks like a mouse. Using 50K pot, 100nFd gives 51Hz low-cut, still good for 82Hz guitar. That will work fine. Or you could scale the cap to compensate how you scaled the pot: pot is half-value so use double-size cap, 200nFd. The difference may be very slight, often moot.

20K would "work" but now you really wanna 5X the cap to keep similar bass with 1/5th the pot resistance. And 5*100nFd= 500nFd= 0.5uFd is a fairly large cap. Since you say you have a 50K handy, I don't see a point in going 20K.

1Meg... any length of cable off a 1Meg pot will shave treble. And the amount of shave is affected by setting. And knob "taper" is strongly affected by next-box loading. A lot of pedal effects use such high-value output pots.

[zombiwoof]

Personally, I would just get the correct pot.  It's only a couple of bucks.  I'm sure you're anxious to get it together, but why not do it the right way?.  Just my "dos centavos".

Al

[dune2k]

I'm sure you're anxious to get it together, but why not do it the right way.

It's just a temporary replacement, the only local electronics store is expensive and's only got sorta crappy pots (plastic shaft...).

Thx to the others.