Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

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guitar-mod
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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by guitar-mod » Sun Oct 16, 2016 12:51 pm

qryss wrote:Firstly: Andy, thanks for interjecting here with some additional help - and thanks in the first place for the circuit! Very much appreciated.
Your welcome qryss. Nice work!!

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by zeger » Mon Oct 17, 2016 10:05 am

guitar-mod wrote:.. I suggest using audio taper for the treble cut (although you may use linear taper), but you really must use reverse audio taper for the bass cut. ..
Hi Andy, Thanks for your great circuit diagram.

One more question though, if you happen to still be reading this:
I understand the Reverse Audio taper pot is the #1 choice, giving the nicest roll-off for the bass-cut (smoothest transition at the beginning of the roll-off). I'm assuming that you have tried using the existing Volume-pot (1M linear mini) that is standard in a jazzmaster rhythm-circuit.

If I would want to wire in the bass-roll-off using this existing linear pot, would it be too sensitive to control? Or, is it okay, but not as smooth as would be ideal?
(With the logarithmic scale inverted, a regular audio taper would probably be even more difficult to control.)

I'm working with a Squier VMJM Alpha mini pot and wondering if I can make do with what I already have. Your ".. really must use reverse audio taper .." made me think maybe there is something else I'm missing.
Thanks in advance!

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by fat finger » Mon Oct 17, 2016 1:09 pm

Audio taper pots kind of suck, especially when you are trying to make a stereo volume control.

Rod Elliot and others have a solution for that, you can turn a linear taper pot in to an audio taper with a resistor or two.

Instead of searching for funky value and taper pots, figure out the math and make them with linear pots and resistors.

In a guitar you are only going for a response that sounds linear, following exact curves isn't critical (and tapered pots don't exactly follow either).

I don't know why anyone would design a circuit with hard to find tapered pots, especially if it makes you drill out your knobs to fit them.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by qryss » Mon Oct 17, 2016 2:56 pm

I kinda get what you're saying. Except the pots aren't hard to find (online) and the real mystery to me is why Fender USA uses 4mm shafts not 1/4" - after all the US is a staunch user of things imperial, no? And Fender Japan uses 6mm shafts; again: why? Makes no sense to me.

:)

I'm not qualified to comment on the use of resistors to change the taper of a pot but from what I've read elsewhere it won't produce the same result in electronic terms (resistances in parallel mean the overall effective resistance varies as you turn the pot) but - as you point out - it's how it sounds that matters.

For some discussion on making your own tapers check this example: http://www.freestompboxes.org/viewtopic.php?f=22&t=8270" onclick="window.open(this.href);return false;

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by Peckhammer » Wed Jan 25, 2017 3:07 pm

fat finger wrote: I don't know why anyone would design a circuit with hard to find tapered pots, especially if it makes you drill out your knobs to fit them.
Well, they are not that hard to find once you know where to look. I now have a bin overflowing with mini pots in 500K and 1MEG values, and with A, B, or C designations (Logarithmic, Linear, and anti-log). Got extra roller knobs that are drilled, and brackets. If anyone is having trouble sourcing this stuff, PM me.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by hpr_hpr » Wed Jan 25, 2017 5:10 pm

Yep that's the nature of reamers as opposed to drills . . . taper . . . and the reason for that is exactly as you found it, to make it as easy as possible to center the reamer in the hole . . . and apply equal pressure to all sides to the hole STAYS centered in the piece.
When thinking about any advice given always ask yourself "why would (s)he know more than I do".

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol

Post by kosta » Fri Jan 27, 2017 9:30 am

Big fan of that PTB circuit here. Happy modding and building! Let us know how you like it. And nice work on those roller wheels!

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by Arty Pop » Sat Sep 05, 2020 12:32 am

I know this conversation is three years old, but in case anybody comes here looking for advice on the PTB mod (that's how I wound up here), I would just like to say that I've successfully widened the 6mm hole in the JM roller knobs to 1/4" using an ordinary (albeit small) round file.

The reamer solution used above looks great, but I couldn't justify spending 30 bucks on a tool that I was going to use for 5 minutes one time. Instead, I used a small round craft file. I just slowly rolled the knob along a piece of wood (traction!) with one hand, gently filing the inside of the hole with the other hand as I went. By keeping the knob in motion, the filing stayed pretty even and the hole stayed pretty round and centered. It took about 10 minutes.

Is the hole perfect? Not if you looked at it under a microscope, but the knob doesn't wobble that I can see. A quarter-inch is only 6.35mm, so you really only have to increase the radius of the hole by 1/6 of a millimeter—take it slow and you'll (probably) be fine.

Anyway, just wanted to offer that additional possible technique for the benefit of future generations of knob-reamers who may read these words.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by Kbcustoms » Sun Nov 01, 2020 5:45 pm

Hi guys. Can't seem to find roller pots for a rothstein ptb mod project.. any pointers? Everyone seems to be out of stock. 👍

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by MayTheFuzzBeWithYou » Mon Nov 02, 2020 1:59 am

Kbcustoms wrote:
Sun Nov 01, 2020 5:45 pm
Hi guys. Can't seem to find roller pots for a rothstein ptb mod project.. any pointers? Everyone seems to be out of stock. 👍
Hey there!
I used this one: https://www.musikding.de/Alpha-Potentio ... 1M-rev-log

They‘re in Germany - but if you don’t want to order some diy pedals along with it, maybe you can at least use the parts name or number if you find one for your search.
Good luck!

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by Peckhammer » Thu Apr 15, 2021 12:16 pm

Search "Black Roller Knobs Preset Controls for Rothstein STB Tone Stack DYI-Kit Jazzmaster Guitars" on Reverb. The kits are restocked every month if they’re sold out.
Last edited by Peckhammer on Sat Apr 24, 2021 5:15 am, edited 2 times in total.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by Fender Fan Boy » Sat Apr 17, 2021 9:22 am

Peckhammer wrote:
Thu Apr 15, 2021 12:16 pm
Search "Black Roller Knobs Preset Controls for Rothstein STB Tone Stack DYI-Kit Jazzmaster Guitars" on Reverb.
Damnit, I missed out in the last one by a freaking day. Wish I saw this post sooner 😢

Does anyone else have any details on obtaining these mythical 1m reverse taper mini pots? I have seriously been looking on and off for a year now. When I finally find a site that carries them, they're all out and never restock. I wish I was savvy enough to figure out another method of doing it with resistors.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by HarlowTheFish » Sat Apr 17, 2021 10:46 am

Fender Fan Boy wrote:
Sat Apr 17, 2021 9:22 am
Does anyone else have any details on obtaining these mythical 1m reverse taper mini pots? I have seriously been looking on and off for a year now. When I finally find a site that carries them, they're all out and never restock. I wish I was savvy enough to figure out another method of doing it with resistors.
If you're stateside, Small Bear has a pretty nuts selection of oddball components, including mini reverse-log pots, so they'll probably have what you're looking for.

My $0.02 though, find a bunch of stuff you need and order it all together, otherwise you can end up feeling a bit like a mug when the shipping is 4/5 of the total cost if you order just the one pot.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by Peckhammer » Sat Apr 24, 2021 5:18 am

Fender Fan Boy wrote:
Sat Apr 17, 2021 9:22 am
Damnit, I missed out in the last one by a freaking day. Wish I saw this post sooner 😢
They are back in stock now.

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Re: Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

Post by Augs » Sun Sep 26, 2021 7:16 am

Yo, I recently completed this mod myself. If anyone is wondering what pots I used:

https://www.amazon.co.uk/gp/product/B08 ... UTF8&psc=1

^ I used those for the Tone circuit and then used the pot that used to be there for the second volume pot.

However, I think I have found a problem or I maybe did something wrong. When you have the pickup selector in the middle, having one of the volumes set to 0 silences the whole guitar instead of just that pickup, essentially both of them are acting as master volumes. Looking at the diagram, I think I understand why this happens.

Image

If I set one of the volume pots to 0 then the resistance from ground to the output of the selector is zero and the whole thing is grounded out. Am I misunderstanding this? Is it possible to wire it so that you can control the volume of each pickup independently?

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