“In 2021 I published a project about a MIDI to CV converter capable of generating up to four control voltages and four digital signals from MIDI messages. It was built around an Arduino nano and a MCP4728 DAC and has been the brain of my DIY paraphonic modular synthesizer for all these years.
Recently I added some functionality to the firmware and soon I found myself with new ideas and enough motivation to take the project back from the drawer and start something new.
I ended up developing a multi control voltage module with eight analog outputs, each having enought resolution to handle notes pitches.
But it’s not only this.
The hardware I layed down can be extended to up to 32 (thirty two!) analog voltages and four more digital outs.
The octaves range, limited to four in the previous MIDI to CV converter, has now been extended to eight.
Being the firmware open source, the code can be modified to handle any sort of incoming MIDI message (note on/off, note number, velocity, pitchbend, aftertoutch, control change, program change and so on) and convert it to a convenient voltage via user definable functions. Is it flexible enought? :)
In this instructable:
- I will show the 8 outs module and how it is layed down
- I will show how easy it is to add additional analog outs
- I will give details about the circuits that make all this possible
- I will share with you all the files needed to have the three (plus one) boards that constitute the module manufactured, thus speeding up the whole build process
- I will share all the necessary files to program it at home with no special devices (thanks Arduino!)
- I will give you hints to realize your module.
Let’s go!
Supplies
Main Board
- 4x PJ324M (stereo or mono) female jack socket
- 1x MIDI DIN 5 (DS-5-01 for PCB mount or DS-5-07A for panel mount)
- 1x MCP4728 12-bit DAC
- 1x 6N138 opto coupler
- 1x TL074 operational amplifier
- 1x CONN 08x2 IDC connector
- 1x DIP-4 switch
- 1x 1N4004 diode
- 1x 1N4148 diode
- 5x 1000 ohm resistors
- 1x 220 ohm resistor
- 1x 330 ohm resistor
- 2x 4.7 K ohm resistors
- 8x 10K ohm resistors
- 4x 100 nF capacitors
- 2x 10 uF electrolitic capacitors
- 1x 8-pin female header
- 1x 11-pin female header
Analog Board
- 4x PJ324M (stereo or mono) female jack socket
- 1x MCP4728 12-bit DAC
- 1x TL074 operational amplifier
- 4x 1000 ohm resistors
- 8x 10K ohm resistors
- 1x 100 nF capacitor
- 1x 8-pin female header
- 1x 11-pin female header
- 1x 8-pin male header
- 1x 11-pin male header
- 1x 3-pin male header
Digital Board
- 4x PJ324M (stereo or mono) female jack socket
- 1x TL074 operational amplifier
- 4x 1000 ohm resistors
- 8x 10K ohm resistors
- 1x 8-pin female header
- 1x 11-pin female header
- 1x 8-pin male header
- 1x 11-pin male header
Calibration Pad
- 4x tact switches
- 1x 8-pin male header
- 1x 11-pin male header”