Read pot value while in circuit?

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JohnRoberts

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Recall capability has been used as poor man's automation when motorized controls, or digital control (full automation) was out of the budget.

This will be rather expensive and a massive undertaking to even add logging capability for mix recall to an existing mixer.

For a much cheaper idea, perhaps a high resolution camera image of the entire mix surface, with a video monitor that allows literal "snapshot" recall and compare capability. You might need to enhance knob pointers to make them more visible in the video images.

Any number of mixer with snapshot recall capability have been manufactured over the years. If serious, perhaps look at some of those schematics. You will likely find extra voltage output on controls, or full voltage controlled mixer functions operated from simple voltage control pots.

Good luck but my friendly advice would be to find a different project. Maybe rehabilitate an old mixer that already has recall capability built in.

JR
 

Golgoth

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Hi JR! I appreciate your input, and you're not the first one to express concerns so I am taking them very seriously.

I have not yet touched the mixer in any way, and am currently gathering as much information as I can. Studying the mixer's circuitry / internal space to get a good objective opinion about the feasability of the project.

I feel very good with a soldering iron and meticulous work so I know I won't be butchering anything. Also the mixer uses pretty cheap guitar pots, so I am not scared of killing one or more expensive vintage potentiometers. Lastly the board only have 16 channels, I would certainly not have considered a mod on a 24+ channel board haha!

I am not in any hurry to mod the desk, and I appreciate the journey learning electronics. Gives me a lot of ideas for future projects! But I would absolutely love to have that recall installed on the desk as it would greatly improve my workflow (I am already recalling from photos and I hate to do it), and might try to implement it when I feel confident about the data I gathered!

Best,
G
 

john12ax7

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If you can get your hands on an SSL X-rack to play with it might give you some ideas on implementation. Each pot and button has an associated LED that changes color when the recall is correct.

As mentioned each pot and switch will need to have an extra section so it will be quite the undertaking to retrofit an existing board. Space will be an issue. You will most likely need to use solder lug pots, so lots of wiring. It might be easier to just build from the ground up.
 

Golgoth

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If you can get your hands on an SSL X-rack to play with it might give you some ideas on implementation. Each pot and button has an associated LED that changes color when the recall is correct.

As mentioned each pot and switch will need to have an extra section so it will be quite the undertaking to retrofit an existing board. Space will be an issue. You will most likely need to use solder lug pots, so lots of wiring. It might be easier to just build from the ground up.
Hi John!

The project actually was inspired by the SSL X-Rack! Thought of buying one of these with summing modules and a bus compressor, but had second thoughts as it is discountinued and I didn't want to end up in a few years with modules full of surface mounted components starting to die..

My current mixer already has solder lug pots used in guitars, I found the same model used for volume with an extra gang of pins so that's encouraging. Still looking for matching references with extra section for the pan pots and pan toggles tho (do they even exist with more than +6 pins each?)!
 

sahib

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3 gang centre detent on a single shaft for pan will be quite difficult. I'll see what I have.

You can get 4 pole double throw toggle switch but you may struggle for space as it is quite bulky. So, perhaps use a SPDT sub miniature type and control again a sub miniature relay. Relay handles the audio and you monitor the switch for recall.
 

kags

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The SSL faders have wipers on each side of the fader's shaft. One side is the audio path and runs against a conductive plastic board and the other side is another conductive plastic board that is used for the automation computer. The large and small faders both worked this way. The VCA and motorized faders (G+ and J/K) had similar layouts, but different motor drives. The G+ faders used a motor (Canon brand!) with a string that attached to the fader shaft and the J/K faders used a rubber track and gear mechanism.
 

Golgoth

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3 gang centre detent on a single shaft for pan will be quite difficult. I'll see what I have.

You can get 4 pole double throw toggle switch but you may struggle for space as it is quite bulky. So, perhaps use a SPDT sub miniature type and control again a sub miniature relay. Relay handles the audio and you monitor the switch for recall.
Thanks a lot Sahib! I'll have a look these options
 

Golgoth

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Golgoth, you never mentioned exactly what mixer you are considering to add the recall functions.

I'm just curious!

Bri
Hi Brian, it's a Chandler Mini Mixer! Pretty basic components / circuit design with a lot of room inside to fit cables and such..
 

Golgoth

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The SSL faders have wipers on each side of the fader's shaft. One side is the audio path and runs against a conductive plastic board and the other side is another conductive plastic board that is used for the automation computer. The large and small faders both worked this way. The VCA and motorized faders (G+ and J/K) had similar layouts, but different motor drives. The G+ faders used a motor (Canon brand!) with a string that attached to the fader shaft and the J/K faders used a rubber track and gear mechanism.
Thanks a lot for the info!
 

Brian Roth

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Hi Brian, it's a Chandler Mini Mixer! Pretty basic components / circuit design with a lot of room inside to fit cables and such..
While I've seen promo info for that, I've never seen one in-person. Can you take some pix of the insides of one of the modules? In particular, the back side of the front panel showing the physical setup with the pots and switches.

Many mixers/desks have the front panel components directly soldered to a circuit board, which makes changing the configuration of the controls extremely difficult....if not impossible.

Bri
 

Golgoth

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I've opened the beast and photographed every millimeter of the insides to study everything. Absolutely brilliant craftmanship throughout! Soldering and cabling is second to none.

Not too happy about the cheap guitar pots and scraped transistors to hide the reference tho..

Here is one dual input card attached, flipped to help me understand the circuit by transparence.

Best,
G
 

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sahib

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I have four and six gang 20kB, centre detent (and centre tapped). They are new.

Four gang will do your job. The third gang is for positional feedback for recall. Fourth gang is unused (unless you have something else in mind).

The shaft is 4mm. So, you will need to use 4mm to 6mm adapter ring which is available off-the-shelf.

Please PM if you think it will work for you.
 

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Brian Roth

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Finding a pot to replace the stock level control (with the attached mute switch) to add the additional position gang will be incredibly difficult.

Bri
 

Golgoth

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Finding a pot to replace the stock level control (with the attached mute switch) to add the additional position gang will be incredibly difficult.

Bri
Indeed, I've only found a version with an extra section for the volume pot itself, not the mute switch part.
 

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Golgoth

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I have four and six gang 20kB, centre detent (and centre tapped). They are new.

Four gang will do your job. The third gang is for positional feedback for recall. Fourth gang is unused (unless you have something else in mind).

The shaft is 4mm. So, you will need to use 4mm to 6mm adapter ring which is available off-the-shelf.

Please PM if you think it will work for you.
Great! I believe the four gang version would be the one I need. I have to check if 20kB is what I have in the mixer!

EDIT: I only need 3 pins on each row actually

Best,
G
 
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Brian Roth

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To refresh my aging memory ("I'm so open-minded that my brains all leaked out! <g>) I decided to dig through a jillion pages of SSL and Amek PDF files I have here. I was just mildly curious about the resistance value of the additional gang used for positional info.

Looks like SSL used a 100K element, while Amek used a 20K gang value. Pondering it all, I can see why a higher R value for the additional gangs makes sense. Those sections have a DC voltage constantly applied across the gang, and hence always draw DC rail power regardless of the physical setting of that gang. In a large desk, that adds up! Less of an issue with a smaller machine such as the Chandler.

Looking at some SSL pot specs, there were really oddball gang combinations, like two sections of one value, reverse log, for actual audio control function ....plus the additional 100K lin for position.

Bri
 

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