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A project log for PolyMod: modular digital synthesizer

A customisable digital synthesizer. Works like an analogue modular synthesizer but cheaper, and with the ability to play many notes at once.

matt-bradshawMatt Bradshaw 08/21/2018 at 21:120 Comments

Some notes on the project that preceded this one.

Earlier this year I finished a digital semi-modular synthesizer and took it to Maker Faire UK. It was unwieldy and inelegant, being a beige MDF box filled with precariously wired breadboards, connected via an Arduino Mega to a laptop which was running a hacked-together soft-synth in Chrome because that was the only way I knew to make a bunch of components talk to a customisable synthesizer.

There's an in-depth video of this project here:

Despite its impracticality, this synth did make some cool noises and successfully demonstrated the concept of using a bunch of multiplexer chips to detect connections between sockets and sending that data to a digital synth. At the end of the video, I mused that a more advanced iteration of the project might be truly modular (containing removable/swappable modules). I was also keen to somehow contain the sound generation inside the instrument itself rather than relying on a tethered laptop: ideally I just wanted a power input and an audio output.

I began investigating the practicalities of on-board sound generation. I had previously completed a big project (a retro synth-guitar hybrid) using a Teensy with an audio board/shield, and was very impressed with its synthesis capabilities, but my earlier research had led me to conclude that dynamically changing the routing between elements such as oscillators, amplifiers, filters etc was beyond the scope of the Teensy audio library. Happily, some further digging revealed this to be false: once I had got my head around pointers and references in the Arduino IDE (something I hadn't had to bother with before), it turned out to be totally possible. Suddenly, a DIY digital modular synthesizer appeared to be feasible.

I promise that the next build log will attempt to approach the present tense.

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