Modding a Volca keys

Hey I was at the Korg forum and I couldnt get an answer for this. Here’s the situation. I want to get a Volca Keys. All the important knob are midi controllable except for the Peak knob…super important knob lol… I was wondering if anyone knows if it is possible to mod it to accept Midi commands for that knob, that way, and editor could be used for presets of all the knobs.

I was thinking… replace the peak knob with a digital pot, then install a second midi in just for that knob’'s midi messages. It’s a lot of work for 1 knob, but does any1 know how to approach this? Or if there is another way?

Thanks for reading

Do you have a schematic? Otherwise it’s going to be difficult.

ahh I looked everywhere, I think Korg didnt release those schematics, all I saw was the Monotron public releases

Look at the pictures it does look like a normal potentiometer. Would there be any reason it may have some secondary purpose that a midi controlled pot can’t replace? It is 3 terminals I believe.

You should check that the digital pot can actually replace the original part. There are a few things to consider:

1. maximum voltage at the three terminals
2. maximum current into/out of the three terminals
3. dynamic response of the digital part (== bandwidth, usually that’s above 100kHz, but it depends on the part)

I would go and open the unit up, leaving the original pot where it is. Then measure the voltages on all the pins, depending on the position of the pot. I don’t know how the pot is used in the schematic, but it most likely has some sort of audio signal running through it. So you will need a 'scope to check the signal on all of the terminals and read the maximum voltages from there. From that you should be able to also calculate the maximum currents into all terminals by ohm’s law.

Then, you can go and select a part that fits your need.

Keep in mind how resonance (“peak”) works on an analog filter, it feeds some of the filter output back into the input. I have a feeling the peak pot on the Keys is a reverse log pot that is ‘in’ the circuit, allowing more filter output into the input. In that case you could control it over MIDI by replacing the pot with a VCA, and controlling the VCA voltage with a small MIDI to cv converter. But, at that point it might be easier to just get a Korg Monologue where everything is already under MIDI control…

Check out the Mutable Instruments Ripples schematic, for example.

Ah thanks for the suggestions. This was definitely helpful and a bit more complex than I perceived. I may hold off on this unit. I prefer the size of it to the monologue, it would be cool if they had a module of it. Perhaps one day I’ll try this out, I just have little spare money to spend on something that might go wrong on my lack of experience in this task.