Looking for over-spec'd pots. Any suggested brands/parts?

[masinyourface]

Howdy all, after a few years absence, the pedal bug has bit me yet again! Right now I'm looking for some over-spec'd pots. I'm not finding what I want on the normal pedal-parts sites, and it seems that I'm too stupid to use DigiKey or Mouser's convoluted search tool. So, here I am asking for suggestions. Any help is very much appreciated!!



In my research, I stumbled across a fairly recent thread that has some great qualitative info:
(https://www.diystompboxes.com/smfforum/index.php?topic=128608.0)

There were a couple suggestions in the thread for TT Electronics pots, like the P09 series:
(https://www.ttelectronics.com/products/categories/potentiometers/potentiometers/?pageNumber=1&orderBy=0&Housing=9).



I guess my main hangups are the longevity of the pots (I've been looking at conductive plastic elements), and that most of the pots I've seen are +/-20% tolerance. So, what would you suggest for a pot that has:

–A robust conductive plastic element for longevity
–Tighter tolerance, so like +/-10% or better
–Vertical PCB mounted
–Standard 6mm shaft

Thanks again!

[Fancy Lime]

Welcome back!

Pots are inherently awful, compared to other passive parts. I have tried and failed to find a practical path around the large tolerances and mediocre lifespan. I learned to live with those as facts of life and directed my OCD elsewhere. The "best" solution I found was what the hifi diy people do. For precision stereo volume controls, they use switches with e.g. 2x24 discreet resistors (hand-matched between the two channels to a fraction of an Ohm because reasons) to form a steppable voltage divider. Combine that with FET soft switching and you have yourself a very precise, long lasting faux pot. Also a huge and expensive one.

Or you can go the much saner route and use switched capacitors controller via a microcontroller to make your own digital pot. That would be precise and long lasting but then you still need a way to control the resistance value. Digital display and capacitive buttons, maybe?

The trouble is that all these things are just so much more complicated than a pot.

Andy

[masinyourface]

That's kind of what I was afraid would be said....although I *think* I might have found two viable options after continued research.



–The Bourns 51/53 series pro audio pots look really nice, but they're only made in either solder tab or horizontal PCB mounted. I could always create a separate daughter-board for pots, however inconvenient it might be......
(https://www.bourns.com/products/proaudio/products)

*however*

–Gorva Design's Variare series pots, although limited in the resistance values available, pretty much has the specs I'm looking for. If I'm interpreting things correctly, the "DuPont POM 500P inner core block" referenced on the website is a conductive plastic element.
(https://gorvadesign.com/products/variare)



I'm going to continue researching this for a bit longer, but unless I find something or somebody gives a better recommendation, I'll probably end up going for the Gorva pots.

[iainpunk]

with my (limited) experience in repairing pedals, i believe board mount and longevity are mutually exclusive. about 10 of the 15-ish pedals ive repaired for friends had failures with board mounted interface. most of em pots and jacks that experienced some outside force and then broke one or more of the surrounding traces. although i don't know if that's because i have friends who handle their pedals quite rough

cheers

[masinyourface]

@iainpunk, that's a great point, and warrants a clarification on my part....in most cases I think mounting pots, jacks, or switches onto PCBs is fine; however, mounting them all on the *same* PCB is a TERRIBLE idea.

My general rule of thumb is to mount pots on one board, and then jacks on a second board with power filtration/relay bypass stuff. I'll then run wires between the two boards and from the jack/power/relay board to a spst switch.

I can see where pots mounted like SMT components could be an issue, but the PCB mounted pots that have pins going through the board have a lot more give and have been fine in my experience so far.

[marcelomd]

IMHO there are two ways to go about reliability here:
- Make it indestructible;
- Make it easy/cheap to replace.

Also, it's best to design something that doesn't depend on really tight tolerances. Like people do with transistors. Lots of ways to not depend on a given hFE, for example.

[MikeA]

–Gorva Design's Variare series pots, although limited in the resistance values available, pretty much has the specs I'm looking for. If I'm interpreting things correctly, the "DuPont POM 500P inner core block" referenced on the website is a conductive plastic element.

500P is Delrin which is a self-lubricating insulator, Gorva doesn't seem to specify the material they use for the conductive track.  Sidebar: Delrin is a common material for guitar picks.   

[ElectricDruid]

I honestly wouldn't worry too much about the tolerance. Why? Because it's a pot! It's *supposed* to be variable!! You just tweak it till it sounds good!

If you can find wire-wound pots in the values you want, they might be a good choice. The "track" doesn't wear out like a typical pot since it's a coil of wire, and the tolerances are often very good. Expect to pay for the privilege, though!

Have a look at this list:

https://www.digikey.pt/en/products/filter/potenciômetros-giratórios-reostatos/84?s=N4IgTCBcDaIO4EsBOBTOB7ArgOwCYAIAHdAFwGcQBdAXyA

[masinyourface]

@marcelomd, agree with you 100%. And your comparison to production spread in BJT hFE is spot on; I'm embarrassed to admit how much time I've sunk into researching different JFET biasing methods over the years to get around production spread . I'm just trying to do my due diligence in the design process to make the best possible design I can. Maybe it's pride, maybe it's OCD; either way I just can't help myself 

@MikeA, you're completely right. When I didn't see Gorva specify the conductive track material, I threw "DuPont POM 500P" into Google, found that it was a plastic, and made the assumption that it was the the material used for the pot's conductive track *without* checking to see how hilariously high the resistance of 500P is. Yet another example of assumptions getting me into trouble..... 




I ended up reaching out to Gorva (hence the delayed reply) and received this back:

The conductive element is carbon, tolerance is +/- 10%
Actually I didn't get the info on life cycles from the manufacturer but we basically maxed out the spec and this is coming from the factory which makes Sony playstation controllers so the numbers should be better than average.
I'll ask about it.

From this and what I've seen elsewhere, I'd be willing to guess that even with the carbon conductive track, Gorva pots should have better longevity than Alpha pots. I'll post an update if Gorva gets back to me about what their manufacturer says.

[masinyourface]

Update time! Gorva just emailed me again:

Just a quick update.
Manufacturer said they have at least 15K cycles.
We haven't done absolute limit test on this model yet but it should be well above 15K.

For reference, standard 16mm Alpha pots are rated for 15K cycles and their 9mm pots are rated for 10K. My curiosity kinda wishes Gorva's contract manufacturer had an exact number, but ±10% tolerance pots with dust covers included that 'will last at least as long as Alpha, likely longer' has me sold enough to buy at least one pedal's worth of pots to test them out for myself.


Thanks for all the replies! Love this community