Read pot value while in circuit?

Help Support GroupDIY:

Brian Roth

Well-known member
Joined
Aug 20, 2005
Messages
1,896
Location
Salina Kansas
Indeed, I've only found a version with an extra section for the volume pot itself, not the mute switch part.
What resistance value and taper is used in the original Chandler design, and what R's and tapers are used in that proposed replacement you posted in the picture?

Bri
 

Newmarket

Well-known member
Joined
Oct 10, 2016
Messages
769
Location
Brighton Sussex UK
In general I think you'll find it v difficult to find what you need - pots with one audio (or log) taper track and one linear track in the specific value(s) required.
Likely need a custom order with associated MOQ and £££s. Or 'DIY' from existing pots - swapping out resistive elements etc.
You could try OMEG or Blore Edwards ? Rotary Switches | Blore Edwards Limited | Wales
Or (sorry to say this) - find a better use for your time and energy !
 

Brian Roth

Well-known member
Joined
Aug 20, 2005
Messages
1,896
Location
Salina Kansas
EGADS!!!! I looked up the pricing for the Chandler mini mixer:


And I am stepping out of further oddball suggestions for adding recall to a boutique $7500.00 device.

Perhaps the OP can find something like a used Shure M68 to begin doing surgery and mods and do "proof of concept" prior to hacking such an expensive unit.


Bri
 

Golgoth

Well-known member
Joined
Jul 24, 2015
Messages
136
Location
France
And I am stepping out of further oddball suggestions for adding recall to a boutique $7500.00 device.
Paid less than half of that price for a 1 year old second hand unit haha!

But I agree, that might still be a bit of an expensive piece to mod for such project and POC..
 

Golgoth

Well-known member
Joined
Jul 24, 2015
Messages
136
Location
France
In general I think you'll find it v difficult to find what you need - pots with one audio (or log) taper track and one linear track in the specific value(s) required.
Likely need a custom order with associated MOQ and £££s. Or 'DIY' from existing pots - swapping out resistive elements etc.
You could try OMEG or Blore Edwards ? Rotary Switches | Blore Edwards Limited | Wales
That's potentiometer heaven! I'll keep that link bookmarked thanks a lot
Or (sorry to say this) - find a better use for your time and energy !
You mean like making music? 😄
 

Brian Roth

Well-known member
Joined
Aug 20, 2005
Messages
1,896
Location
Salina Kansas
Like I said, find a Shure M68 (inexpensive in the used market) and then try doing a POC with it. If you mess up, No Biggie! That project I'll follow with interest since I've never messed with Aurdinos (sp?) and I'll learn something.

Bri
 

Brian Roth

Well-known member
Joined
Aug 20, 2005
Messages
1,896
Location
Salina Kansas
Try try again:


Bri
 

Golgoth

Well-known member
Joined
Jul 24, 2015
Messages
136
Location
France
Try try again:


Bri
What's happening with the comments? lol

I'll try find an M68 or equivalent, might be difficult to find here in Europe. I'l keep you updated Brian!
 

Golgoth

Well-known member
Joined
Jul 24, 2015
Messages
136
Location
France
@Brian Roth I have been thinking, what if I based the recall on the output volume of each channel?

One could set up a simple group in the DAW sending a 440hz sine wave at a fixed level to each individual channel, read every channel's outputs (L/R), then save these values instead of the pots values as initially planned.

No more pot replacement to do, only need to somehow plug to the outputs pins of each cards. Of course the Mini Mixer does not have individual outputs that could have made the implementation immediately possible, but wouldn't that solution be easier to implement than the one previously thought about?

The flow would be a little heavier than being able to screenshot the knobs position at any given time but I feel that it's still so much easier than taking a picture to recall from when working on several sessions every day.. Just need to pause the track 10 seconds and send the sinewaves through..

Do you think that would be doable regarding the pictures of the boards I sent you? Is my belief that it is possible to somehow plug to the audio channel without doing any harm to the audio (when using the mixer to mix normal audio) to read the volume correct or am I mistaken?

I can even imagine a beautiful plug and play recall kit for Mini Mixer's owners to plug into each channel's connector!

Best,
G
 
Last edited:

Newmarket

Well-known member
Joined
Oct 10, 2016
Messages
769
Location
Brighton Sussex UK
@Brian Roth I have been thinking, what if I based the recall on the output volume of each channel?

One could set up a simple group in the DAW sending a 440hz sine wave at a fixed level to each individual channel, read every channel's outputs (L/R), then save these values instead of the pots values as initially planned.

No more pot replacement to do, only need to somehow plug to the outputs pins of each cards. Of course the Mini Mixer does not have individual outputs that could have made the implementation immediately possible, but wouldn't that solution be easier to implement than the one previously thought about?

The flow would be a little heavier than being able to screenshot the knobs position at any given time but I feel that it's still so much easier than taking a picture to recall from when working on several sessions every day.. Just need to pause the track 10 seconds and send the sinewaves through..

Do you think that would be doable regarding the pictures of the boards I sent you? Is my belief that it is possible to somehow plug to the audio channel without doing any harm to the audio (when using the mixer to mix normal audio) to read the volume correct or am I mistaken?

I can even imagine a beautiful plug and play recall kit for Mini Mixer's owners to plug into each channel's connector!

Best,
G

Assuming the pots are log / audio taper then there would be possible issues with resolution of reading a non-linear taper. But if those limitations are acceptable I guess you could look at it.
What sort of fader resolution are you thinking of and over what section of fader if not all ?
 

john12ax7

Well-known member
Joined
Oct 14, 2010
Messages
1,944
Location
California, US
You wouldn't necessarily need direct outs. As long as the channels are independent, e.g. the settings on Ch 2 don't influence Ch 1, then you could successively apply tones and read the master L/R level. Or you could even do all channels simultaneously by using different frequencies on each channel.
 

Golgoth

Well-known member
Joined
Jul 24, 2015
Messages
136
Location
France
You wouldn't necessarily need direct outs. As long as the channels are independent, e.g. the settings on Ch 2 don't influence Ch 1, then you could successively apply tones and read the master L/R level. Or you could even do all channels simultaneously by using different frequencies on each channel.
John! Sending different frequencies to each channel is a brilliant idea! Genius even.

Furthermore I believe that with your solution everything could be done ITB, maybe within the DAW itself. I think that the solution is so simple that setting an analog to digital reader up with an arduino as initially planned would be too much of a hassle. Everything could already be set in the session template I use when working on a new session. I may need to code a dedicated plugin but to be honest I am more at ease with programming than electronics so that would be fun!

I'll mod a simpler mixer as suggested by @Brian Roth for a first project!

I will experiment and report back!

Thanks again for that elegant solution!
G
 

john12ax7

Well-known member
Joined
Oct 14, 2010
Messages
1,944
Location
California, US
If you are good at programming that makes things a lot easier. You would need to experiment regarding accuracy, but there are two possible approaches you could take. 1) Match the levels at each frequency (channel), or 2) Flip the polarity and do a null type match, where you adjust the gain pots until all the frequencies disappear.
 

Winston OBoogie

Well-known member
Joined
Jun 3, 2004
Messages
2,684
Location
UK.
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

What you see on that board is two output amps from the TG12410 series. The original transistors were 2N4910 and 2N4891.
See the limiter schem for the circuit. The input to these inverting amps on your mixer will be via a fixed resistor rather than adjustable. Standard was about 15K for 10dB gain.
 

Attachments

  • TG Limiter 1969 Schematic.pdf
    486 KB · Views: 20

Golgoth

Well-known member
Joined
Jul 24, 2015
Messages
136
Location
France
What you see on that board is two output amps from the TG12410 series. The original transistors were 2N4910 and 2N4891.
See the limiter schem for the circuit. The input to these inverting amps on your mixer will be via a fixed resistor rather than adjustable. Standard was about 15K for 10dB gain.
Great information thanks! I didn't know the Mini Mixer's channels were based on that Limiter circuit. Do you have other TG schematics?
 

Winston OBoogie

Well-known member
Joined
Jun 3, 2004
Messages
2,684
Location
UK.
Great information thanks! I didn't know the Mini Mixer's channels were based on that Limiter circuit. Do you have other TG schematics?

It's not the limiter circuit per se, it's the output amplifier circuit that was used in the modules built for the TG12410 mastering/transfer desks.
You can find a couple more schematics (TG12414) in the tech docs section on here.

For the various circuits used in the TG12345 recording/mixing desks, there's a thread on here that has them - search for TG Diagrams.

I haven't checked inside one myself but, from the pic you posted, it doesn't appear that Chandler's mini mixer is based on the actual mixing desk design.
If you posted a pic of the master mixing section, maybe we could identify it. It's possibly also another output amp.
That amp in itself would be a pretty good virtual earth mixer so, are you sure the mixing is passive?
 

Latest posts

Top