Pot identification

[LuckyD]

Can anyone identify this purple encased pot? It's in a one off build I bought used. I'm not going to mention the name of the maker. No need, I don't think. Pretty sure it's an audio taper pot, on a phase 100 clone.  Is this standard? Wondering if I should swap it out. I do have to swap the rotary switch. It's making some really terrible crunching sound when switching. But that's easily accessible. The speed pot is not.

Just wondering if there is anything to be gained from switching to a linear taper?

[moid]

Welcome to the forum

GuitarPCB sell violet pot condoms; it does look like one of theirs:

https://guitarpcb.com/product/the-original-pot-condom/

Someone else with more knowledge than me will need to answer your other questions though!

[idy]

Welcome.
Yes that is a pot condom, or dust cap. They fit over any pot that size.

"Pretty sure" it's audio taper? Why?

I think phase 100 uses 500k "C" taper or reverse log, not unusual for "speed" on LFOs. Using linear would mean it would be slow through most of the travel with all the faster settings "bunched up."
But if it is using an audio or "A" taper, then a linear or B might actually be better...

[LuckyD]

"Pretty sure" because all the action happens at the end of CW. It took me a while to wrap my head around it. Thankfully I was at least aware of audio taper. So after a deep dive on pots last night, and schematics, it appears that phase 100 do seem to use reverse log pots.

So, all that said, the quickest jump when you cycle through speeds happens at the end of the throw, CW. And please correct me if I'm wrong (I probably am) I would see the quickest cycle through speeds at the beginning CCW of a reverse log pot, correct?

And for added fun, I have an MXR Block Phase 100 coming this week. That the person believes is faulty, but I am guessing they didn't understand the pot situation.

Thanks for the help.

Pot skirts? Who knew!

[ElectricDruid]

So, all that said, the quickest jump when you cycle through speeds happens at the end of the throw, CW. And please correct me if I'm wrong (I probably am) I would see the quickest cycle through speeds at the beginning CCW of a reverse log pot, correct?

Not necessarily, because it depends on how the LFO responds too, not just the pot.

Imagine the LFO responds linearly, so that halving the resistance is required to double the frequency. Ears being musical things, we'd typically want equal octaves for a frequency control, so we'd need a pot that goes 500K - 250K - 125K - 62K5 - etc in equal amounts of rotation (e.g. a Rev Log pot)
If we put a linear pot in, we get 500K - 400K - 300K - 200K - 100K - 0K in equal amounts of rotation, so the first octave uses up half the sweep of the control, but the next octave only uses 1/4 of the range, and the next octave after that only uses 1/8th (etcetc).
So you can see that a *linear* pot can give you frequencies all bunched up at the end.

[duck_arse]

pull it out. read the pot markings. A? C? B?

also welcome.

[printer2]

Indica.

[LuckyD]

pull it out. read the pot markings. A? C? B?

also welcome.

It's far too buried in there to bother with that. And of course, the purple dust cap doesn't help. But I'm sure the dust cap was because it's in such close proximity to everything else in there. And pretty much under the PCB.

Now onto that rotary switch....