super cheap and effective (USB)MIDI - CV converter (10V,15V...) using only the power of USB
The idea came to me when I quickly needed a (USB)MIDI to CV converter (10V) and was "inspired" by looking through my dusty electronics boxes. The result is an extremely simple interface that also runs stably – without any fluctuations. I assume you have some coding experience, meaning this is just a sketch, not a complete guide:
You will need (besides the usual capacitors, resistors, and diodes):
- MCU (I'm currently using RP2040 boards)
- SPI/I2C DAC: at least 12-bit, like the MCP4922, MCP4728...
- OpAmp: doesn't have to be fully rail-to-rail, but at least 0V = 0V should be equal, like the LM358, LM324...
- A cheap step-up module from China like the MT3608 Step Up
- A cheap step-down module with a trimmer, like the MH-Mini-360
Example for 0-10V:
Classic setup: MCU -> DAC -> Opamp (2/1 ratio)
The 5V from the USB port is stepped up to ~12-14V (depending on fluctuations) using the MT3608
Now the key:
Using a step-down converter With the MT3608 (MH-Mini-360), I can precisely adjust my output current. To do this, set the DAC to its highest level and check the voltage at the op-amp's output. Use the trimmer on the Mini-360 to adjust it to the exact desired output (10V in this example).
This way, the MT3608 provides enough buffer for current fluctuations to bring the high voltage down to the precise voltage using the step-down converter.
What was initially intended as a "workaround" works so flawlessly (no measurable ripple!) that I now use it in virtually every prototype circuit.
This is a fast draft of my MIDI-CV-interface:
Posted Mar 10, 2026, 11:21 AM UTC