mixers with recalleble EQ settings?

[tony666]

Most of these 'totall recall' analogue mixers are to expensive for me but I was wondering if the following exists : a mixer wich stores the settings by measering the impedance of the potentiometers (like a voltmeter). When you move the potentiometer a led bliks when you come near that impedance setting. This way you can store the settings of the EQ but you have to make the settings by hand when recalling a previous mix?

This would not be that difficult to make or am i forgetting something?

 

[kambo]

arduino with decoders, works great.

 

[JohnRoberts]

While not cheap you could make EQ using DPOTs (digital controlled pots) and control the EQs with a micro. Not trivial to develop an interface to display status and recall presets.

JR

 

[Andy Peters]

Most of these 'totall recall' analogue mixers are to expensive for me but I was wondering if the following exists : a mixer wich stores the settings by measering the impedance of the potentiometers (like a voltmeter).  When you move the potentiometer a led bliks when you come near that impedance setting.  This way you can store the settings of the EQ but you have to make the settings by hand when recalling a previous mix? 

This would not be that difficult to make or am i forgetting something?

Define "difficult." Seriously.

You'd need to use dual pots, with one track for the actual EQ/gain/whatever setting, and the second has a DC voltage across the two ends. A micro can have ADCs read the voltage at the second wiper for the position. This is tricky when you need a dual pot to implement the circuit, so you'd need a custom three-gang pot.

Then there's the small matter of software to store the settings and then tell you how to get them back.

 

[gyraf]

So no, it's not difficult.

Just quite expensive, and a lot of work.

Jakob E.

 

[warpie]

Define "difficult." Seriously.

You'd need to use dual pots, with one track for the actual EQ/gain/whatever setting, and the second has a DC voltage across the two ends. A micro can have ADCs read the voltage at the second wiper for the position. This is tricky when you need a dual pot to implement the circuit, so you'd need a custom three-gang pot.

Then there's the small matter of software to store the settings and then tell you how to get them back.

How do you deal with the tolerance error between the two gangs?

 

[audiomixer]

That's no issue:

the sensing pot has a defined value at each angle (besides start and stop where it becomes a tad trickier).  he rotational angle is now represented in an ADC value. the actual value of the 'operating' section of the potentiometer is not of interest, it just follows because its wiper is at the same position. you can even have different tapers for the sensing part and the acting part. your microcontroller does not need to know the true ohmic value in your circuit.

some faders have different tapers for audio (log or audio taper) and sense or VCA (10k lin) for the automation.

- Michael

 

[gyraf]

You don't have to deal with tolerance - it's the same pot it reads out into...

Jakob E.

(edit:synchro post)

 

[warpie]

Ah yes, true…

 

[kambo]

actually, u dont even need to use additional gang... you are not gonna store your movement of your pots over a period of time... u only need to store fixed position of pots. so
u can use the same pot.
once u ready to store your settings, just disconnect the pots from the circuit, and
feed some DCV( 3-5vdc). and store that value to micro... when u want to recall, do the same...
you only need to read one gang...

"disconnect the pots from the EQ circuit," : i am not an electronic expert, but you would need relays and some fixed value resistor to keep eq safe, ... it may damage your board... experts will explain better...

on some old SSL recall boards, when u do recall, u run a recall software and, you dont really run audio through...
u switch to audio, after your setting done...

only drawback, when u need to store your your setting, ( which is press of a button) no audio should be active... but who cares...
that solves your getting custom pot problem on 3 gangs... but a lot of relays...


ps: you would need additional gang, if you are doing flying faders... as u need to record pot value over period of time....

pps: for 3-5 VDC. as i am not expert in audio electronics... u may need to use smaller value, 3-5 vdc might be too much for pots life ???... experts will tell you better on that value...

ppps: when u ready to store, u may not even need to bypass the pots... just bypassing audio could work too...
not sure, if feeding small DCV would damage any circuit in this case... experts 

 

[kambo]

While not cheap you could make EQ using DPOTs (digital controlled pots) and control the EQs with a micro. Not trivial to develop an interface to display status and recall presets.

JR

i would go with JohnRoberts suggestion... digital pots are easy to deal with... if u r good with programming... as u dont get them in log rev log etc .... u have to program ur micro for it...

my first suggestion of using encoders ( i typed decoders for some reason - late night )
is a cheap way if u good with mechanical connections.... coding micro for it is way easy....

i am using digital pots with encoders on my high speed camera arm. works great, and super accurate.

 

[JohnRoberts]

I did some development work on a digitally controlled analog product, and I was favorably impressed with the audio performance of modern DPOTs (the early ones had some serious issues). That said the economy of putting all that effort into a digital interface, and then the added expense to perform the function using analog circuitry seems like a very expensive way to accomplish the task to satisfy a niche customer preference.  As digital adds more and more features for less and less cost, the business proposition becomes harder to sell.

While a digital pot works pretty well, you can perform a simple multiply inside the digital domain (to control gain/level) in one clock tick.

If we get to the point where the control interface becomes a smart phone app, doing the whole thing digitally becomes even cheaper.

I am an old analog dog, and really wish analog was better,  because I still have unfinished ideas, but even with my analog bias I can not even convince myself.

JR

 

[Andy Peters]

"disconnect the pots from the EQ circuit," : i am not an electronic expert, but you would need relays and some fixed value resistor to keep eq safe, ... it may damage your board... experts will explain better...

on some old SSL recall boards, when u do recall, u run a recall software and, you dont really run audio through...
u switch to audio, after your setting done...

only drawback, when u need to store your your setting, ( which is press of a button) no audio should be active... but who cares...
that solves your getting custom pot problem on 3 gangs... but a lot of relays...

It's been a long time since I used it, and I used it just once (the Whiskey in LA, easily the loudest show I ever mixed!) but I think the Langley Recall live-sound desk had that. I honestly don't remember whether the audio was active when you were recalling.

But it had Rupert Neve's voice in the cans saying "more more ..." as you turned each knob on the desk, so I guess that's a bonus.

Yeah, switching the audio out and applying a DC voltage across the pot is horribly expensive in terms of board real-estate and complexity, and there's the not-so-small matter of muxing the wipers of each pot to however-many ADCs you need to read them.

ps: you would need additional gang, if you are doing flying faders... as u need to record pot value over period of time....

Yes, or use an encoder track and note the position digitally.

pps: for 3-5 VDC. as i am not expert in audio electronics... u may need to use smaller value, 3-5 vdc might be too much for pots life ???... experts will tell you better on that value...

For the pot values commonly used in a mixer, 5 V is fine. Do the math. 5 V across 5k is 1 mA. Of course, given that a lot of the multichannel ADCs you'd use these days, as well as the ADCs included with your favorite micro, a 2.4 V supply might be better, to match the ADC input range.

ppps: when u ready to store, u may not even need to bypass the pots... just bypassing audio could work too...
not sure, if feeding small DCV would damage any circuit in this case... experts 

I wouldn't do that.

 

[SSLtech]

on some old SSL recall boards, when u do recall, u run a recall software and, you dont really run audio through...
u switch to audio, after your setting done...

No.

Never.

SSL never did this to my knowledge.

You are almost certainly confusing the fact that SSL used to "share" TR data over the automation lines, and had switchover gates to route the data, but they NEVER shared signal pot gangs.

And you could always run audio through every single control while recall was active. Nothing was ever shared.

Likewise the Langley Recall and Big consoles.

COULD you use the same gang? -Yes. as described. And it could certainly work.

...but it wouldn't work during recall, and I doubt that you could ever sell such a product without being utterly destroyed by client reaction once they realized that their console could do one thing or the other -either pass signal or run recall- but not do both at the same time.

Rupert's voice was fed onto the AFL buss. Amek -like Neve and others- always used an additional linear gang on every pot. The only products that used the same gang for control and recall were 'DCA' products like the Euphonix, Trient Di-An, etc.

 

[kambo]

on some old SSL recall boards, when u do recall, u run a recall software and, you dont really run audio through...
u switch to audio, after your setting done...

No.

Never.

SSL never did this to my knowledge.

i didnt mean to sound like an expert
i was referring to my own experience of recording session... we always had to wait,
until the engineer, recalled the whole console.

COULD you use the same gang? -Yes. as described. And it could certainly work.

...but it wouldn't work during recall,

i am confused on this, are you referring to adding relays to pots, or using same pot without relays,
while audio active ?

and I doubt that you could ever sell such a product without being utterly destroyed by client reaction once they realized that their console could do one thing or the other -either pass signal or run recall- but not do both at the same time.

waiting while recalling the console,  didnt really matter if console ran audio through or not, , manually adjusting every single pot and pressing buttons on huge console takes time... and you wanna concentrate on twisting
knobs, not really do anything else...

surely its better to have recall and audio at the same time, but
i dont see any huge advantage just because u cant do both at the same time...
besides, no audio on recall,
doesnt mean whole console is mute...
its CH at a time...

micro's are cheaper now, and getting cheaper

 

[SSLtech]

I was responding to your suggestion that the same pot gang could be used by 'switching' from audio function to "DC-Read" function, (which would mean that the audio would not be able to pass).

The fact that an engineer wasn't willing to start a mix until the recall was completed doesn't mean that this is an acceptable outlook, nor that this should be reasonable. -This is not the ONLY use of recall, either. -Back in the 80's, I used to run recall while tracking. I'd store cue mixes 'just in case'. there would be all sorts of times when recall would be activated while still passing audio.

Same for broadcast or other applications. Somewhere there will always be a power user who will want to push what a unit can do.

Plus... adding dozens or hundreds (or thousands) of switches interrupting signal in a console WILL eventually start to have an effect on the sound. -SSL found this even with their gold-plated sub-assembly edge connectors. -Having hundreds of connection points interrupting a signal path would 'conspire' to effect the sound subtly, and people didn't like it. -If one were to add to that further switching points -whether relay or 'sand-state'-  there would almost certainly be a further distrust in the purity of the signal integrity.

 

[kambo]

this is a "CH mute on recall" type mixer... and its free to think about

worrying about  pcb mounted relay on every pot gonna effect my sound in my DIY project... no 8)

if you think as an industrial solution, yes... i agree with most... but then, i will be using encoders anyway...