Voltage-Controlled Volume Control

[eleanor296]

Heya guys,

currently messing around with stuffing a bunch of pedal guts into a 1U rack and controlling it all via MIDI.

I was looking to put a volume control in my amp's serial FX loop and control the thing via an Arduino, i.e. voltage.  Got any recommendations for circuits to look at?

I'm having a hard time searching for this topic, simply searching for "volume" gives me everything, searching for multiple applicable terms barely returns anything.

[LiLFX]

Digital potentiometer?

[eleanor296]

That's the brute force way I guess.  Wonder how smooth that'd be.  LED/photocell pair might be another option?

[balkanizeyou]

you can use a designated VCA chip (VCA - voltage controlled amplifier).
Or you can search for a discrete VCA design, there's plenty of that on the web (using a LM13700 is a simple way of doing this for example)

[PRR]

> control the thing via an Arduino, i.e. voltage.

That's a computer. You can indirectly get a voltage out of it, sure. But bit-banging a digital volume control is more natural. A 256-step control is smooth enough for almost any audio purpose.

[merlinb]

LED+LDR combo, digipot, LM13700, THAT2181, PGA2310, MUSE72320, MDAC, relay array... welcome to my world.

How quiet does it need to be? How many steps? How accurate? How much 'kill' do you need? What taper? How expensive?

[Ice-9]

Have a look at something like the Analog Devices AD5252 non volatile I2C digital pot IC's.

[DDD]

LED+LDR definitely is a winner (LED driver should be inertial to avoid scratches from the control pot).
*** Total consumption is about 3-4 mA, that is enough for LED.

[eleanor296]

LED+LDR combo, digipot, LM13700, THAT2181, PGA2310, MUSE72320, MDAC, relay array... welcome to my world.

How quiet does it need to be? How many steps? How accurate? How much 'kill' do you need? What taper? How expensive?

Sounds like I got some homework to do.

I'm also stuffing a wah in there, seems it's pretty much the same problem/solutions.  Don't mind it costing a few bucks, especially if it's a solution that's simple to implement.

[eleanor296]

Have a look at something like the Analog Devices AD5252 non volatile I2C digital pot IC's.

Eyyy bingo, looks cool.