What do you do if you want the convenience of MIDI but the warm tones of analog synths? Build a MIDI to CV converter, of course! In this project, you'll use a QT Py RP2040 running CircuitPython with an MCP4725 DAC to convert MIDI messages to a gate output and 1V/oct output.
The build is housed in a snazzy 3D printed skull adorned enclosure. The output jacks are located in the skull's eyes.
The CircuitPython code converts MIDI
NoteOff messages to gate out and 1V/oct signals that are sent through the two mono audio jacks. This lets you play your CV controlled synths with a MIDI keyboard or a MIDI song file from your DAW.
The MCP4725 DAC is a digital to analog converter and outputs the voltages to correspond with the expected 1V/oct value.
1V/oct is a standard for controlling pitch in modular synthesis. A volt is divided to correspond with the twelve pitches in western music. For example, 0.333V is pitch E-2 and 0.917V is pitch B-2. When the voltage is increased by 1V, the octave increases by 1. For example, 1.333V is pitch E-3 (an increase of 1V and 1 octave) and 2.917V is pitch B-4 (an increase of 2V and 2 octaves).
However, these pitches are approximate and depend on a variety of factors, such as your oscillator's tuning and any electrical interference. But that's half the fun of synthesis!