Stereo (dual gang) push-pull or push-push potentiometers (for filter based / Wal style pramps)

[Kinkh]

Hello!
First post here ;D

First off, I did search the forums, but either I'm incompetent or there really isn't any thread of this kind...

To start off, I'm building some multi coil pickups and a filter based preamp for me and some of my friends (for now). The main problem for now is that if one doesn't want to drill extra switches for separate frequency control and Q control, you'd have to use one pot for everything (like on a Wal). That means a dual gang pot with a push-pull switch and C taper (anti log). These type of pots seem to be extremely rare.

The question is, what are some of the sources for pots like these? The pot needs to be dual gang and have a push-pull or push-push switch. Preferably C taper, but A works as well (wired in reverse it's C but CCW reduces frequency instead of rising, which is counter intuitive but works ). Haven't tried B taper though.

Here is a list of some that I have found so far:

1. Bourns PDB183-GTR22 - available at Mouser. Only 250k and 500k and A taper available.
2. Bourns PTM902 series - available at mouser. Various options available.
3. MEC - makes custom pots as per customer request. Available at Banzai Music. Kinda expensive (50~60€). Also looks very much like the one i a real Wal bass.
4. Alpha Taiwan RD902B22F. I have seen it only in their catalogue, but I can't find any sources. It seems like Lusithand Devices use them one their preamps though.

Do any more of these types exist and where can they be obtained?

Thanks in advance for any answers!

 

[Passinwind]

Hello!
First post here ;D

First off, I did search the forums, but either I'm incompetent or there really isn't any thread of this kind...

To start off, I'm building some multi coil pickups and a filter based preamp for me and some of my friends (for now). The main problem for now is that if one doesn't want to drill extra switches for separate frequency control and Q control, you'd have to use one pot for everything (like on a Wal). That means a dual gang pot with a push-pull switch and C taper (anti log). These type of pots seem to be extremely rare.

The question is, what are some of the sources for pots like these? The pot needs to be dual gang and have a push-pull or push-push switch. Preferably C taper, but A works as well (wired in reverse it's C but CCW reduces frequency instead of rising, which is counter intuitive but works ). Haven't tried B taper though.

Here is a list of some that I have found so far:

1. Bourns PDB183-GTR22 - available at Mouser. Only 250k and 500k and A taper available.
2. Bourns PTM902 series - available at mouser. Various options available.
3. MEC - makes custom pots as per customer request. Available at Banzai Music. Kinda expensive (50~60€). Also looks very much like the one i a real Wal bass.
4. Alpha Taiwan RD902B22F. I have seen it only in their catalogue, but I can't find any sources. It seems like Lusithand Devices use them one their preamps though.

Do any more of these types exist and where can they be obtained?

Thanks in advance for any answers!

Try Omeg in the UK. At best it’ll likely be a special order with a ten unit minimum order quantity. Dual C taper pots without a switch for my open source filter preamp design ran about $12 per unit including shipping a month or three ago. They are working out really well so far in my test bass, FWIW.

 

[Kinkh]

Try Omeg in the UK. At best it’ll likely be a special order with a ten unit minimum order quantity. Dual C taper pots without a switch for my open source filter preamp design ran about $12 per unit including shipping a month or three ago. They are working out really well so far in my test bass, FWIW.

Thanks!
Great to know that they can make small batches of custom pots. 12$ is reasonable enough. Sadly enough, they don't offer any dual switched options when customising, at least not directly through the website customizer.
Do you think it would be worth a shot to contact them directly with this inquiry?

 

[Passinwind]

Thanks!
Great to know that they can make small batches of custom pots. 12$ is reasonable enough. Sadly enough, they don't offer any dual switched options when customising, at least not directly through the website customizer.
Do you think it would be worth a shot to contact them directly with this inquiry?

I would definitely email or call them. The two salespeople I dealt with were great, it was a very old school experience all the way around.

You could also post about this in my fairly active thread here, if you’re so inclined: The Passinwind Open Source Preamp

 

[Kinkh]

I would definitely email or call them. The two salespeople I dealt with were great, it was a very old school experience all the way around.

You could also post about this in my fairly active thread here, if you’re so inclined: The Passinwind Open Source Preamp

Sure, I wouldn't mind posting over there. About which part should I post though? That thread i huge (and also very useful, thanks for that ), and I wouldn't want to clutter it with unrelated stuff

 

[Passinwind]

Sure, I wouldn't mind posting over there. About which part should I post though? That thread i huge (and also very useful, thanks for that ), and I wouldn't want to clutter it with unrelated stuff

How about just letting us know what Omeg say? Lots of us over there would be happy to get their hands on pots like that.

 

[dwizum]

Arrow has the PDB183-GTR22 but also only in 500k. What resistance value do you want?

 

[Kinkh]

How about just letting us know what Omeg say? Lots of us over there would be happy to get their hands on pots like that.

Ok. I'm gonna contact them tomorrow and get back with whatever info I get.

Arrow has the PDB183-GTR22 but also only in 500k. What resistance value do you want?

Resistance doesn't matter, I can just recalculate everything else based on the pot. The smaller value the better - less noise in the end.
I'm gonna add Arrow to my supplier list, thx for pointing them out. Shipping is a bit expensive, but I might need them some time, you never know!

 

[dwizum]

If you sign up for their rewards program, shipping is free over some fixed amount ($50 I think). I've been bouncing between digikey and mouser for 20-ish years of hobby electronics products but just recently have switched almost entirely to Arrow since they seem to have good selection, good prices, and fast shipping.

 

[Kinkh]

Does that apply just to US or worldwide? I'll look into it, thanks for the info!

EDIT: Found it! Free DDP shipping to EU if for orders over 50$ if I'm not mistaken.
Now that's a real life saver

 

[andare]

Have you tried Tayda and Digikey?

 

[Kinkh]

Tayda doesn't offer any switched pots, and Digikey has everything Mouser does (except it's all out of stock) as listed in first post.
Thanks for the help though!

 

[ardgedee]

I haven't shopped for pots yet, but for other items I've had more success at getting hobbyist-scale quantities of things from Arrow than from Mouser.

 

[A9X]

What are the switches on the pots for?

 

[Kinkh]

What are the switches on the pots for?

They turn on/off the high Q mode (~10dB boost at corner frequency)
Here is a graph for better explanation:

I haven't shopped for pots yet, but for other items I've had more success at getting hobbyist-scale quantities of things from Arrow than from Mouser.

I haven't done business with either. Up until recently getting goods from US/UK/EU was painfully expensive and almost impossible on a hobbyist scale. I ordered mostly from Asia.

 

[Passinwind]

They turn on/off the high Q mode (~10dB boost at corner frequency)
Here is a graph for better explanation:
View attachment 4472768



I haven't done business with either. Up until recently getting goods from US/UK/EU was painfully expensive and almost impossible on a hobbyist scale. I ordered mostly from Asia.

I think my friend in The Netherlands said Mouser only required a $25 order to get to a reasonable shipping cost as of fairly recently, I’ll double check on that the next time I talk to him. I use Mouser and Digikey the most but have occasionally seen Arrow stocking parts that neither of them had.

 

[A9X]

They turn on/off the high Q mode (~10dB boost at corner frequency)

I know how an SVF works, I just didn't know how you were implementing it. My Alembics used variable via a pot or 3 position in a separate switch which seems far more useful to me than a single setting. My current version is variable like the one's I've built in the past or an Alembic S2.

 

[dkelley]

I recently (like a couple months ago or more) finished building my own alembic series 2 style filter preamps. two of them (on the same board, sharing power supply components). Unfortunately, as I opted for the constant variable q knobs, I didn't take into account that the gain would be audible much higher with the q turned up. I'm trying various dual gang pots so I can coincidentally lower the gain while increasing the q pot, but have had trouble finding the right pots for the job.

frustrating! But I mean, all that said, it works great.

However, my system is setup in a very me-friendly, but everyone else alienating, way:
q and frequency knob for neck pickup, q and frequency knob for bridge pickup, pickup blend (mixer) knob for blending the outputs of the two filter preamps, which then goes into a third preamp - a 3 band - so I also have bass, mid, and treble controls, and then a master volume.

It's the most versatile bass I've ever played. But the radical volume changes of the q controls really is frustrating. If I changed them to switches then I could balance the level with fixed resistors (or trimmer pots internally), but I really want the variable q thing.

I need to sit and work it out, but honestly I'm just done LoL. The issue with the dual pots for level control during q changes is that the rate needs to be different for level control versus q. linear q pot and log (ish) level compensation pot. And I haven't found those anywhere.

 

[ardgedee]

I wonder if it's possible to disassemble a few pots and take the resistance tracks out to build what you need.

 

[eloann]

I wonder if it's possible to disassemble a few pots and take the resistance tracks out to build what you need.

I've seen it done to pots that were out of the desired tolerance