Version 0.1 from August 2021
Digital polyphonic synth lead on breadboard. I build it while having some slack time, waiting for new DIY kits for my techno rack project. The idea is taken from the Chord Organ from Music Thing Modular.
- ✅ 4 simultaneous voices (polyphony)
- ✅ 5 different waveforms: sine, triangle, square, saw and “tuned” noise
- ✅ 13 different chord shapes (major, minor, 7th, …)
- ✅ 48 semitones (from C-2 to C+2)
- ✅ CV IN for the root note (1 volt per octave)
It is based on an Arduino Nano. Luckily I found the library the_synth. That made the implementation with some additional circuitry a relatively easy task.
The logic and design of the chord shapes are taken from the Music Thing Modular’s approach. They can be edited in the code.
- Remove noise and crackling:
- This is the elephant in the room. Especially in lower tone regions you can here it. I guess this is related to the software. So far I opened an issue in the repository of the fundamental library, let’s see. Fixing it by myself would be beyond my programming skills and I would rather go for building the original Chord Organ.
- A portion of the noise can be filtered by additional circuitry or following filter modules. But of course this comes with costs for the dynamic range as well.
- The noise is most noticeable with the sine and triangle waves. With the rest of the waves, it almost gets lost in the overtones.
- Add a CV IN for the chord shape, just like the original module has one.
- Add an opamp at the end for amplification
- Implement it as an Eurorack module on stripboard or PCB.
Also see the comments on Instagram, Reddit and Mod Wiggler.