Schatten Thumbwheel Alternative

[jorgemg1984]

Hi!

I need a small pot to use with my soon to be new archtop. I have now realized these are called thumbwheel pots... I need a 1M log pot on this format. I just need volume, no tone, and just the pot on the thumbwheel format, all the remaining electronics will be done by my tech. Any suggestions?

The schatten ones seem great but expensive and I don't need two pots (or the wire).

[Jonathan0996]

Mouser.com has all the thumbwheel pots you could possibly want. I bought a couple from them once and everything went smoothly.

[jorgemg1984]

Thanks Jonathann. But maximum value is 100K... right? Which value did you used?

[jorgemg1984]

If I get a 1M resistor can I sub the resistor on a 500k thumbwheel pot? Is this doable?

[Jabberwocky]

* WD Music Products - 500K THUMBWHEEL POT

500KOhm though.

[PTChristopher2]

>>> If I get a 1M resistor can I sub the resistor on a 500k thumbwheel pot? Is this doable?

What do you mean? Can you draw the schematic of what you propose to do?

[Jabberwocky]

You could also have 1MOhm pot in a small box wired outboard in between a 1/4" plug and socket. Plug one end to your guitar jack. Plug your guitar cord in the other.

Not ideal but short of finding a 1MOhm thumbwheel pot which does not seem to exist it looks quite viable.

Yet another option is to have an outboard attenuator with discrete resistors. This allows you to step through discrete values of resistance and hence discrete changes in volume. How coarse or fine you want it is up to you. The finer it is the larger the number of discrete resistors required. Holco or Vishay resistors are what's popular with audiophiles.

[jorgemg1984]

Chris: Turning a 500k pot into a 1M one.. maybe a stupid idea by someone who does not have a clue about this stuff?

Jabber: Good idea but maybe I'll just go with the 500k and be done with it... It's just I've done enough experiment with electronics to know 1M it's the value I like!

[Jabberwocky]

Cool. Glad you found your solution.

[jorgemg1984]

Just another stupid question... two 500k pots in parallel will yeld a 250k load. Would two 500k pots in series yeald an 1M load? Would both volumes worked wired this way?

[PTChristopher2]

This is so much easier to do with schematics (much as music is easier to technically describe with musical notation), but I guess we are using text.

The volume pot is not a simple resistor that variably turns the guitar signal into heat thus reducing its electrical strength.

A volume pot is set up so that its impedance is matched to the output of the PU. One end is hot and the other is ground. You now have a continuum from maximum signal (in principle anyway) to zero signal along the resistor inside the pot.

In practical terms this continuum is not at all linear.

The center wiper of the pot allows you to tap into this continuum as you see fit.

To turn a 500K load into a 1M load, you would need to add your 500K resistor on one end or the other of the pot. This would the only allow you to sweep the center wiper along part of the continuum. Further, the wiper would short to a point 1/2 way along the continuum.

In practice it would not provide a reasonable volume control in my opinion.

If you prefer running the PU with a 1M load and can only have a 500K pot, then you could add a switch that added a 500K resistor in series with the pot. You would then short out the resistor any time you wanted to use your volume control. While this would work, it strikes me as somewhat absurd.

All in my opinion.

[jorgemg1984]

My tech will add a 500k resistor and solve the issue

Many thanks all for the help!!

[PTChristopher2]

And where exactly will he put this resistor?

1. Between the hot end of the pot and the hot end of the PU? This will give you a max volume setting similar to a "9" or "8" on a 1M pot. And where will the hot at the output jack be connected? You could argue for either end of the 500K resistor. Will you measure the actual sonic benefit to this configuration vs. a simple 500K volume setup? I suggest of course actually having real non-interpretive info about the results. (This can be unpopular in the mist-filled world of "tone".)

2. Between the ground end of the pot and the ground end of the PU? (This assumes that the ground end of the pot is then lifted 500K off ground.) This will give an odd mismatch of impedance at the guitar output and a limited range to the now-pseudo volume control.

3. Some other location?

I am curious about this Quixotic plan to show a 1M load to your PU while having a usable 500K volume pot.

Anything remotely like a schematic would of course be far better than a description subject to remarkable confusion.

If this is a cooperative forum, then some actual detail here would be quite helpful to covering this subject.

[jorgemg1984]

I don't have a clue about how he will do it but he says he will... If he has the time and patience (highly doubt it) I'll ask for a schematich.

[Woody Sound]

I just googled

1MOhm thumbwheel pot

and got lots of items.

[jorgemg1984]

Thanks Woody, I had done the search with 1M and nothing. Should have reminded me of doing it with 1 meg ohm..

[PTChristopher2]

>>> I don't have a clue about how he will do it but he says he will... If he has the time and patience (highly doubt it) I'll ask for a schematich.

I understand. It is nonetheless a limiting aspect of such a forum when the seemingly unlikely is mixed into a technical discussion.

It happens.

I have seen plenty of 1 meg trim pots, but these would have to be retrofitted with some skill to incorporate the sort of large-ish ergonomic thumbwheel that we have become used to in guitarland.

Or maybe a unicorn can sprinkle magic dust on one,...

Chris

[Jabberwocky]

I just googled

1MOhm thumbwheel pot

and got lots of items.

They are mainly trim pots. Trim, Loctite and forget. Not practical for audio use.

Perhaps a pickguard-mounted 1MOhm audio pot won't be such a bad idea if you can abide pickguards.

Or my off-the-Harvey-Wallbanger suggestion: Mount the 1MOhm pot in the upper rim, the way a strap button is mounted. None would be the wiser to it with a discreet knob.

[PTChristopher2]

>>> They are mainly trim pots. Trim, Loctite and forget. Not practical for audio use.

Although I put it in a far more obnoxious way, that is also my opinion of the easily available 1M pots.

On the other hand, they would probably stand up reasonably well to the sort of careful use to which a Jazz player is likely to put it.

Also, for a custom guitar, one could set up the hidden mount to accept a PC board mount 1M pot, then add a larger thumbwheel.

So maybe buy three pots and setup the mount and retro-fit thumbwheel for easy replacement of the pot. This would make for a likely lifetime+ solution. Just keep the identical pots in a small container inside the case for eventual spares.

But I am still cranky about hypothetical impedance matching (for all that maters),...

And to be unfairly critical of a "too busy for your understanding" luthier: Part of the job of customer service is to be able to simply and clearly explain what you are doing and why it will accomplish the goal.

********************

The essence of General Relativity can be explained in about 80 seconds, including practical experiments.

"String Theory" wallows in endless (like decades of) rambling conjecture with no single proposed experiment.

I just am predisposed to what works, and the reason behind it. This is likely a character flaw.

Chris

[jorgemg1984]

No pickguard, it will be inside the f-hole.

Chris I appreciate a lot your help but no need to go that way. My luthier is a great friend of mine and I don't even think in terms of "customer service"... he would explain it all to me if I wanted, which I don't. I said he was busy to draw a schematich of his solution and post it here not busy to explain it to me.

Anyway I will probably just use 500k pots and be done with it. As a musician I know 1M volume pots and no tone control work well for me (I tried several solutions), that''s why I wanted to know if it was possible to mod the 500k one. One day I might found why I like the 1M more but I've been enjoying magic more than reason lately.

[murrayatuptown]

I agree completely that putting a fixed resistor in series with a smaller value pot, as questioned above, creates several possible annoyances. Off topic (not asked about), but related, is when someone desires a lower value pot resistance and wonders if paralleling the full fixed pot resistance with another value (say one parallels the full pot (not the wiper) with a fixed value of equal value (say a 500k pot paralleled about the upper and lower terminals with a 500k fixed resistor...yes, the resistance presented to the pickup will be half that (250k), at a certain rotational position, but not others.

This is also ignores the fact that non-wire-wound potentiometers are generally not very precisely close to their marked value. That is a small matter compared to how screwed up the taper (linear, log, reverse log, or special %R vs % rotation historically preferred by amp and guitar manufacturers) becomes

Even a linear pot altered this way ends up with a none-of-the-above tapers. I have wasted a lot of time (or learned something?) measuring what happened to a pot I tried paralleling with an equal value. I didn't believe what I measured and still cannot explain why it affects the wiper to either end-terminal the way it does. Then I wasted more time trying to make sense of it with a spreadsheet. It doesn't keep me awake at night any more...I just don't do it unless I don't care about the range of adjustment vs rotation. There are situations where you don't care, but volume & tone are not the scenarios where you don't care.

Precision linear pots, if they are made anymore, are usually wire-wound instead of carbon or cermet (ceramic metal) composites. They were uncommon, if even made at such large values like 500k & 1M. But they lasted much longer and the linearity was the critical goal.

I just bought a Schatten dual set and forgot (until just now) something I learned the hard way in a different industry than guitar.

If you compare datasheets for a 'real' potentiometer with a shaft and mounting bushing and trimmer potentiometers (usually small with a screwdriver adjustment vs. shaft & knob), a 'real' pot has a rotational life rating of something like 10000-20000 turns. Some trimpots may have rotational life rating of as low as 200 turns! They are not meant for daily use but in circuitry where they are adjusted once during alignment or calibration, then rarely or periodically if there is a need or requirement. The exception to low rotation ratings for trimpots are multi-turn types, which infrequently were wirewound and disappointingly expensive. (I needed 20-turn Bourns trimpots that happened to have gold-plated leads for repairing something made in the mid-80s, and they were about $30 each about 8-10 years ago :O( )

A thumbwheel pot is arguably a trimpot by construction, with a thumb wheel and a poorly supported rotor (compared to a bushing-mount knob-pot).

I doubt there is a known trend for thumbwheel pot failure, but if actually there IS, and I was ignorant of it, there is a likely reason for it.

A thumbwheel volume pot probably get a lot of use. A thumbwheel tone pot might have less wear & tear.

That WAS a lot of of money to spend and talk myself out of installing!

Just be more gentle with thumb pots and don't torque them at an angle other than their designed rotation by putting pressure on the rotating disc.

Or no one has ever, or ever will, have a thumbwheel pot wear or fail prematurely, and you can call me krazy.

M

[murrayatuptown]

Look at the cost of Alpha thumbwheel pots ($1.61 each in single quantity) in late Oct. 2024 at Mouser.

You can find shaft pots that cheap, but I don't think anyone wants the cheapest pots they can find for guitars or amps.

So I wish a long and trouble-free lifespan for us thumbwheel pot users...but I don't have a good feeling about it.

[Bobby Timmons]

^ If OPs don't respond to brand new threads they start, they ain't replying to 10 year old ones. :P

[murrayatuptown]

That is true, but undead threads are useful sometimes. You (I) just never know when.

[GuyBoden]

I've been looking recently too.

There are some cheap Thumb wheel pots on Ebay, that don't look robust, to say the least. (They would last about 2mins. Approx)

These: