Still doing a few other things first before I dive in the deep end, but I have started tinkering,, they are far too expensive to buy, so yes its DIY Vactrols.
Because I intend to build quite a few, I have ordered 50 LED's, 50 LDR's, next was to find an acceptable build, I have gone with and led with end sanded flat, glued to an LDR with a tiny bit of clear silicon, then into clear heat shrink, then positioned into black plastic tube (outer casing of a cable) just big enough to fit, then both ends sealed with molten black wax. No testing done yet.
Plan is as follows.. Axo will send midi data to an arduino nano, which will interpret and send instructions via I2C to a PWM module, the PWM will then be filtered into a voltage, then connected to the LED of the vactrol. I ma waiting for the PWM module to arrive, as well as a simple midi shield for the nano.
The following are the challenges of concern.. 1 being of most concern.
1. The PWM to voltage filter, there are so many online, many will need to be tested to find out which is the best.
2. Vactrol as voltage divider, getting the correct circuit for this is essential to control the Audio.
3. Vactrol as adjustable resister, this is straight forward but as it is likely to be used to replace pots in an effect pedal, I am thinking of easy way to just unplug a pot and plug in the vactrol.
The reason why I chose this over digipots, cheaper, and it seams a lot easier to do large volumes. The PWM module will have 16 PWM outs, and as many as 96 pwm modules can be connected together, but I won't need that much.
I will start slowly, first with just on / off type control, then adding in parameter like control.
A lot of work to get through..