MIDI to Hertz per volt converter (korg CV)

Hey Everyone,

I want to build a MIDI to Hertz Per Volt converter with an arduino. I know how to do everything except the hardware circuit that would come out of the analog reads. Does anyone know off the top of their head what it would look like?

The range is 16V, so I would need a separate power supply, which is no problem. BUT how would I divide the voltages with the 0-5V output from the arduino analog reads? Would I use a type of transistor attached to the 16V line? Any advice or thoughts would be appreciated!


  • It’s MIDI to Hz/V so why do you need analog reads?
  • Don’t use the arduino “analog” output - they are PWM and not accurate enough.
  • Use 3 digital pins to drive a SPI DAC. Amplify it wih an op-amp to go beyond the initial range of the DAC, which will be under 5V anyway.
  • Don’t go with the full range of 16V since you’ll need a lot of precision. Go with a smaller range, 8V or even 4V - this reduce by 2 the number of bits required on the DAC. Hz/V is quite unforgiving since small errors in the mV range do matter a lot in the lowest range.

Thank you, amazingly helpful as usual pichnettes!

Could the CVPal firmware be reworked to do this (not by pichenettes obviously)? Ignoring the USB part, could one channel be input and another output?

I’m not sure what we’re trying to do here.

V/Oct CV to Hz/V CV conversion?

Or MIDI to Hz/V conversion?

And what kind of MIDI is that? USB-MIDI or good old 5-pin DIN MIDI?

But in the case it’s V/Oct CV to Hz/CV, the answer is no, you can’t do that with the CVpal. If you want to do that with a MCU (which is a rather silly idea), you’d need accurate AD and DA converters, at the very least 12-bit. And op-amps to scale/protect the input and outputs.

Will the Shruthri read hz/v CV natively from an MS-20?

AFAIK the shruthi will only read MIDI natively, much less CV of any kind.

You could probably modify it to respond to CV of your choosing, but it sounds like an expensive way of controlling a shruthi…

thanks, then it is not for me!

maybe grab a korg sq-1 as a workaround?

Very few synths respond to Hz/V, I’m not entirely sure that there are many(if any) DIY synths that do.

Get an English Tear or Disting Mk3 module and connect it to you MIDI to CV converter
why reinvent the wheel

As all my synth are Hz per volt, and as I own zero volt per octave, there is nothing to reinvent! One nice synth is the monotribe as it reads either!

Also, I do not use midi. All 100% live with no computer.