ER-301 Sound Computer


The ER-301 is a voltage-controllable canvas for digital signal processing algorithms. One of the many characteristics that attracted me to modular synthesizers is that they enabled me to make the kind of music that I love away from the computer. However, not all digital audio tools can be elegantly and efficiently realized in a dedicated hardware form. So, I either had to deny myself those tools, or, go to the computer.


  • Live virtual patch creation without stopping the audio.
  • A core library of patchable units covering various functions from the simple (mixing, VCA, envelope generation, limiting, filtering, etc.) to the complex (loopers, granular synthesis, variable-rate sample playback, wavetable oscillator, etc.)
  • 512MB of RAM, with about 480MB available for memory-resident samples. All memory-resident samples are converted to 32-bit (float) but keep their original sample rate.
  • Loads samples of any sample rate and bit depth (as long as they are WAV files).
  • Records up to 12 tracks of audio/CV to the SD card in the background.
  • Package Manager for easy sharing of patches, presets, custom units, and third party libraries.
  • There is a growing collection of user-developed units.
  • The firmware and SDK are open-sourced on GitHub. Users can develop their own units using the mid-level (Lua) SDK for maximum patching flexibility, or, using the low-level (C++) SDK for additional performance and custom graphics.


  • Width: 30hp
  • Depth: 35mm from the back of the faceplate including the ribbon cable
  • Current Consumption: (+12V/-12V/+5V) 250mA/30mA/0mA
  • 2 monochrome OLED displays where the smaller display shows additional context for the focused element in the main display.
  • The main knob is a high-quality optical encoder rated to over 1 million rotations.
  • 4x audio (AC-coupled) outputs configurable to 48kHz or 96kHz at 24-bit.
  • 4x audio (DC-coupled) inputs sampled up to 60kHz at 16-bit depth.
  • 12x CV (DC-coupled) inputs sampled up to 60kHz at 16-bit depth.
  • 4x gate (DC-coupled) inputs sampled up to 96kHz at 12-bit depth.

:warning: Read this before you purchase :warning:

  • Firmware is still under heavy development which means frequent updates and bugs. The good news is that typically any bugs found are fixed within a few days.
  • The documentation is always lagging behind the firmware development. The forum is usually the best place to get answers these days.
  • All 4 outputs are AC-coupled, therefore, no CV output. (Gasp! The horror!) This is a purposeful design decision to focus the ER-301 on sound generation. If you think even 10-minutes about what a modulation computer would look like, I think you would agree that it is not the ER-301. :wink: