Dual Concentric tone pots.

[B.Flat]

I am hoping to consolidate two tone pots to a single dual con. pot , but the original values are bass 20K and treble 100K. The only odd value concentric pot I have found so far is a Fender 250/500K version.

Can anyone suggest a solution to the problem or point to a supplier. I have to add that my electronics knowledge is sparse, so layman's version please !

[obbm]

It is possible to take apart and rebuild CT dual pots.  You need to get a dual 250K/500K and the matching singles of the required values, strip them all down remembering what goes where and rebuild very carefully.

[itu]

To find an exact copy of the thing you are after is a somewhat difficult task. But if you can do searching and soldering, something can be done. Start from this:

https://www.diystompboxes.com/smfforum/index.php?topic=66471.0

This should give you an idea how to change the other pot from 100 k to 20 k.

 

Then go to Digi-Key. Their selection has dual pots - only if you can find them. The helping column here is "Actuator diameter" under "More Filters". Search for those that have two diameters. And 100 k.

https://www.digikey.co.uk/products/en/potentiometers-variable-resistors/rotary-potentiometers-rheostats/84

Lin/log was not specified, but hope this helps.

[rmorris]

12 hours ago, obbm said:

It is possible to take apart and rebuild CT dual pots.  You need to get a dual 250K/500K and the matching singles of the required values, strip them all down remembering what goes where and rebuild very carefully.

+1. I doubt whether 20K / 100K is a readily available combination. I reckon the only realistic way to get what you want on a one off (or even small / moderate basis) without spending "mortgage money" is to build it from existing potentiometer component parts.

[Hellzero]

Here you can have it made to measure : https://www.banzaimusic.com/Custom-Pot-Duplo.html

Edited September 24, 2018 by Hellzero

[rmorris]

3 minutes ago, Hellzero said:

Here you can have it made to measure : https://www.banzaimusic.com/Custom-Pot-Duplo.html

 

Interesting - although it comes to 48 Euro for a pot inc shipping (I'm assuming OP is in UK).

I see they offer three tapers - although need to check what they are as letters to denote can be inconsistent. I guess for tone it's linear but you never know.

There's no 20K option but there is 25K - maybe that's close enough for the OP ?

Also - it doesn't mention the track composition - so I guess Carbon.

It might be worth contactin OMEG in the UK to see if any response ?

[Hellzero]

These are made by MEC, I ordered a very specific one some 15 years ago and it's still working.

Yes, for tone and active circuitry linear is the right option.

25k will be ok, as it's only a 20% tolerance which is good for this purpose.

Alpha was offering a similar product years ago, but it seems to have vanished.

[Hellzero]

Found what you're looking for, and it's made by Alps :

https://www.ebay.co.uk/itm/ALPS-Precision-2X-DUAL-20K-Linear-Taper-100k-Potentiometer-9-5mmX11mmX17mm/122482891716?epid=844959373&hash=item1c848c9bc4:g:kpsAAOSwjL5ZDkbi

[B.Flat]

Thankyou obbm, itu, rmorris & Hellzero, I am grateful for the fast and informative replies, thank you again.

One way or another the problem has been solved by you, and I will let you know how it turns out.

The bass is Japanese and the pots ref. letter is G for the active tones and D for the volume. I am assuming this is G = Linear, D = Audio. Can anyone confirm ?

[itu]

http://www.resistorguide.com/potentiometer/#Marking_codes

They may be year codes, so manufacturing dates or similar, too.

[rmorris]

11 hours ago, itu said:

http://www.resistorguide.com/potentiometer/#Marking_codes

They may be year codes, so manufacturing dates or similar, too.

Yes - as it says :

"different standards uses the same letters which can be confusing"

so you need to consult the datasheet or manufacturer / distributor.

[rmorris]

21 hours ago, Hellzero said:

Found what you're looking for, and it's made by Alps :

https://www.ebay.co.uk/itm/ALPS-Precision-2X-DUAL-20K-Linear-Taper-100k-Potentiometer-9-5mmX11mmX17mm/122482891716?epid=844959373&hash=item1c848c9bc4:g:kpsAAOSwjL5ZDkbi

What are the chances 😊

So there are actually four gangs there - 2x20K and 2x100K.

I guess that you can just use one of each as long as it fits mechanically.

[Chienmortbb]

Don't trust leter codes for the pot law (taper) The UK standard was A linear B Log.  The US standard was A Log (or audio) B Linear. Different manufacturers use different codes though.

[Passinwind]

On 24/09/2018 at 04:44, Hellzero said:

Here you can have it made to measure : https://www.banzaimusic.com/Custom-Pot-Duplo.html

Noll offers custom MEC pots like that as well. They are far from cheap.

[B.Flat]

On 25/09/2018 at 11:43, rmorris said:

On 25/09/2018 at 11:50, rmorris said:

What are the chances 😊

So there are actually four gangs there - 2x20K and 2x100K.

I guess that you can just use one of each as long as it fits mechanically.

Thank you for the link. I did look but it seems psychically too small, both for the D.Conc. knobs I have and the mounting hole in the body. I know there are ways around this but I am now looking at replacing the passive vol & tone with a d.c. pot. Both are 500k I will have to sacrifice the log/lin parameter but I have a dual 500k log pot which should not be too bad, what do you think people ?

 

[Count Bassy]

On 25/09/2018 at 10:43, rmorris said:

Yes - as it says :

"different standards uses the same letters which can be confusing"

so you need to consult the datasheet or manufacturer / distributor.

I would like to second this.

I once made the mistake of reading a date code (7812 - i.e. December 1978) as the part ID and replaced a power transistor with a 12v voltage regulator (same package type). Remarkeably it actually worked for about 4 hours. Unfortunately this meant that my mistake was found by someone on the night shift rather than by myself.

[rmorris]

On 26/10/2018 at 21:57, Count Bassy said:

I would like to second this.

I once made the mistake of reading a date code (7812 - i.e. December 1978) as the part ID and replaced a power transistor with a 12v voltage regulator (same package type). Remarkeably it actually worked for about 4 hours. Unfortunately this meant that my mistake was found by someone on the night shift rather than by myself.

FWIW if I saw '7812' on a TO220 package I'd assume it was a +12V regulator too 😃

[Mottlefeeder]

You can convert a linear pot to a lower value log pot by ptting a resistor between the wiper and one end of the track. A fixed resistor value somewhere between 1/4 and 1/6 of the value of the track will get you fairly close. That suggests that a 100K twin pot could give you a 100K linear and a 20K log pot.

Not sure if that helps.

David

[B.Flat]

Thank you all for replies and advice.

The reason I was doing this mod was to enable me to add a Stellartone Tonestyler without having to drill more holes in the body.

I am now considering an alternative circuit by replacing the passive vol. & tone with a dual concentric (which I already have in the correct values).

The Tonestyler works independently from the passive tone and I was wondering if, when the tone pot is fully open, it no longer effects the circuit tonally or in any other way. If yes would a simple switch cutting the hot wire to the vol pot make it invisible to the circuit ?

I was also going to add a treble bleed to the vol pot but am unsure what values of resistor and cap to use. The pickups are P & J with three position toggle, no blend.

Any comments or advice?

[itu]

If you have this switch, do you need anything else? You could do studio version, i.e. no pots, only switches.

Three position mic switch, tone switch & vol switch (which is also On/Off). Can be done with a multiple position rotary switch, like:

Off - quiet & tone On - loud & tone On - loud & tone Off - quiet & tone Off - Off (6 positions)

OR

loud & tone On - quiet & tone On - Off - quiet & tone Off - loud & tone Off (5 positions)

Or just one switch for tone and a step attenuator. I have maths for a step attenuator if you want to do quite a few solderings...

[itu]

Life saver: http://alexplorer.net/guitar/mods/shock.html

[B.Flat]

On 02/11/2018 at 19:29, itu said:

If you have this switch, do you need anything else? You could do studio version, i.e. no pots, only switches.

Three position mic switch, tone switch & vol switch (which is also On/Off). Can be done with a multiple position rotary switch, like:

Off - quiet & tone On - loud & tone On - loud & tone Off - quiet & tone Off - Off (6 positions)

OR

loud & tone On - quiet & tone On - Off - quiet & tone Off - loud & tone Off (5 positions)

Or just one switch for tone and a step attenuator. I have maths for a step attenuator if you want to do quite a few solderings...

Hi itu.

You've lost me a bit there. What I am hoping to do is use the Tonestyler as the basic tone shaping and then use the passive tone as  "depth" of tone , all as suggested by Stellartone.

The Tonestyler has a bypass setting, so the original wiring (passive tone only) is achievable. What I want it to know if the passive tone is basically "out of circuit" at ten, delivering Tonestyler only, or do I need to switch it out to achieve this. Oh what a tangled web we weave !!!

 

[itu]

So sorry, sir.

Let's play it again: I gave you but too many ideas. Some studio guys have these switch based P-basses with two switches: on/off, tone on/off. That is probably the simplest configuration that exists. It also provides straight line from pickup to board without any pots or tones in between if needed.

Stellartone's solution is close to the all on solution but has more sound options, too. I am pretty confident that you would be happy with it.

If you are not after the very trebly sound, this studio type on/off -thing is probably not yours. Anthony Jackson's Fodera has just the pickup and an output jack. He will have some high end rack effects and a studio mixer after the bass and cable. That's why he doesn't need any cheapo adjustments in his bass.

[B.Flat]

14 hours ago, itu said:

So sorry, sir.

Let's play it again: I gave you but too many ideas. Some studio guys have these switch based P-basses with two switches: on/off, tone on/off. That is probably the simplest configuration that exists. It also provides straight line from pickup to board without any pots or tones in between if needed.

Stellartone's solution is close to the all on solution but has more sound options, too. I am pretty confident that you would be happy with it.

If you are not after the very trebly sound, this studio type on/off -thing is probably not yours. Anthony Jackson's Fodera has just the pickup and an output jack. He will have some high end rack effects and a studio mixer after the bass and cable. That's why he doesn't need any cheapo adjustments in his bass.

No need for apologies, just got the wires crossed, which is a very apt euphemism. Why? Because I have the bass all wired up, exactly according to the published Ibanez diagram, working perfectly ok EXCEPT the passive tone and volume are working  anticlockwise.

I assume that reversing the connections to the outer legs of the pots should remedy this ?

[itu]

Yes, that should fix the issue.