Finished CVPal

The CVPal. An Open Source USB (MIDI) to CV Interface.

  • Based on open source circuit designs from Mutable Instruments
  • 5VDC over USB operation
  • Provides 2 programmable Gate and CV outputs
  • Programmable through .syx files over MIDI


The CVPal is an awesome little utility discontinued by Mutable Instruments several years ago. The project is Open Source, so the schematics, board files and firmware are still available. I downloaded and reviewed the files, and determined that this would be a very quick build, made of inexpensive parts. I sent the PCB computer files off to Osh Park to be made. Osh Park is located in the USA, and accepts all orders online. They then place your order into a batch of others, so a large PCB panel will have dozens of different circuits for various people. That is how they are made inexpensively. They also ONLY COME IN PURPLE. You had better like purple. I paid $22 for 3 boards shipped to my door. Took about 3 weeks.

Assembling the PCBs

Assembling them is very straightforward, and for a processor they use the Atmel ATTiny which cost about $2. The design allows for maximum flexibility for use, and even provides a small prototyping section for adding or extending the design. I had a half dozen of these StarTech RS232 to Ethernet interfaces laying around. I had used the 9VDC adapters for a dozen other projects so these were perfect. I gutted the two circuit boards from them and salvaged some of the components like the power connector, USB port, etc. If you are going to stay in DIY, collecting stuff like this saves the planet and your wallet.

Gutting the case

Once I figured out how the PCB would fit and be secured into the box, I added the 4 jacks. The PCB allows for board mounted jacks or free wire (as shown). I don’t like board mounted jacks as they can easily break unless secured in some other manner.

Adding the jacks

Then make the appropriate cutouts, decorate and paint it the way you want and… here you go!

A CVPal pair

These are perfectly identified the moment you plug them into the system. From Ableton live, I can select the interface box as an ‘External instrument’, and send a midi track down that channel. I can even send separate MIDI commands, like a ‘Note on’ to CV out 1 and CC commands out to the CV output 2.