Squareinator is a 3-operator plus noise monosynth based on the SN76489 sound chip - the same chip as used in early '80s video games and computers. It gets its name from the fact that the SN76489 produces square waves (and pseudo-random noise). But square waves alone would be boring - that's why there's a nasty 12 db/octave multi-mode voltage controlled filter (VCF) on-board. VCF envelopes are driven by a 12-bit DAC, so they're very smooth, even at the longest envelope settings. The filter is capable of self-oscillation in all filter modes (lowpass, bandpass, and highpass).

Squareinator code runs the chip as a monosynth. There is ADSR control over the VCA (via the onboard 4-bit attenuators) and ADSR control over the VCF. Each operator has an independent level control. Squares 2 & 3 have detune and octave controls. There is a simple on-off LFO for the VCA with depth control, as well as pitch bend and glide. Glide is selectable as legato or always on. VCF cutoff note tracking can be enabled, allowing the filter to be played at full oscillation.

Squareinator is driven completely by MIDI CCs. Why? Knobs are expensive, that's why! You probably already own a MIDI controller with knobs, or have a MIDI sequencer capable of handling CC changes. There's a single button for setting the MIDI channel; press once to enter set mode, press to count to MIDI channel, hold to set - LED blinks back the channel to confirm. Power-cycle to run with the new channel.

Boards sold here are ready to run. Just add a pjrc.com Teensy 2.0 microcontroller. Use the Arduino 1.x IDE plus Teensyduino to upload the code found on github to your Teensy 2.0 and you're ready to play. CCs are documented in the source code.

This is a very limited edition of three (3) boards. Once these run out I will be offering bare boards for those wishing to build their own. A BOM is available on the github repo.