EL-ONE (Donut)

What features does your synth have? Yes.

Donut started as a passion-project-turned-dream-synth. The current outline of features includes:

• 5 Sources:
  • Wavetable oscillator
  • Additive waveshaper
  • Slimmed down tensions implementation
  • Particles: a granular experience
  • Sampler instrument
• 4 Modulators:
  • Morphing LFO
  • 4-point envelope (ADSR, point-to-point)
  • Random generator with various quantization features
  • Sequencer
• 4 Filters:
  • Lowpass filter
  • Highpass filter
  • Bandpass filter
  • Comb filter
• 4 Effects:
  • Reverb
  • Stereo delay
  • Wavefolder
  • Glitch

Demos

I made a few demos using the software prototype. They are listed here:

• devlog I
• devlog II
• devlog III

Software

The Donut firmware for EL-ONE is completely custom, written in C++, and can be compiled to run on macOS and Linux. Future releases will include hardware implementation, right now it only runs as a CLI application. Donut uses jackd as its audio backend.

A web-based patch editor for the system is also available. It can be found at editor.donut.layetri.net.

Hardware

EL-ONE is based around the Raspberry Pi 4B. Hardware design is currently in progress, however a few details are listed here:

• 7" central touchscreen
• 4 separate sections for the different categories (sources, modulators, filters, effects)
  • One rotary encoder for circular input
  • One 0.9" OLED display
  • Four or five tactile switches (with LEDs?)
• 61 key keybed (salvaged from a Yamaha PSR-280)
• 16-bit DAC (TDA1543A, unless I can find something better that isn't out of stock)

Getting the whole thing

The software implementation can be found in this repository. Once I finish the hardware design, I will provide it for free through my website, however I will ask anyone who wants to build it to leave me a little message (in case anyone ever sees this or wants one for themselves, I'd love to know).

Build instructions

To build the firmware available through this repository, you should first make sure you have all the necessary dependencies installed. These are the requirements for building Donut:

• ncurses, libncurses or your platform's equivalent
• libjack2-dev headers available globally
• gcc version x and up
• cmake for completeness' sake

First, generate build files from the project root:

  cmake .

Then, use CMake to build the project:

  cmake . --build

Finally, to run Donut, first start jackd. Once JACK is running, run the program from the project root folder:

  ./CMakeFiles/donut

NOTE 1: make sure to run Donut from the project root folder! This is where it looks for its runtime resource files (like wavetables and presets).

NOTE 2 (Linux only): before running Donut, make sure there's a MIDI connection available through something like a2jmidid.

Thanks and stuff

• The default piano sample was generously provided by Björn Colin
• This project uses open source code from the following repositories:
  • ocornut/imgui
  • nlohmann/json
  • adamstark/AudioFile
  • thertk/RtMidi
  • hanickadot/compile-time-regular-expressions