MATRIXSYNTH: GumpherDM3 Arduino Based DIY Hardware Chiptune Synth

Thursday, February 02, 2017

GumpherDM3 Arduino Based DIY Hardware Chiptune Synth

Uploaded on Jan 19, 2017 GumpherDM3

"This is a MIDI capable Arduino controlled monophonic semi-modular analog synthesizer. It has 4 VCOs (2 Audio, one Sub-audio and one hybrid that switches between either), a 4-pole low pass filter, a Voltage Controlled Amplifier (VCA) and two envelope generators (AR1 and AR2). It also has an arpeggiator built in to add some videogame-esque sounds. My awesome wife printed out the decals using the Silhouette Cameo and transferred them onto the wooden control panel with a layer of Modpodge to make it scratch resistant. I never really sat down to figure out how many octaves it can work with before the tuning goes bonkers, but it appears to handle six octaves pretty well.

I hope you enjoy the video. I had a really great time learning about this stuff and actually getting to build a working synth.

Tech Stuff: The VCOs, LPF and VCA cores are all built around the LM13700 OTA using mostly datasheet schematics with component values adjusted to work on +-9V supply. Also, since the synth uses the LM13700 for all VCOs and VCF, all exponential current sources use PNP transistors. I added in my own design for input CV signal mixing to the modules and output signal normalizers (to produce both CV and audio signals). I attempted to design my own CV generator using the Arduino and while it works more-or-less, I learned first hand about the challenges with using the PWM analog signals produced by the micro-controller as CV signals for the synth modules. I don't think I would do anything differently in this project, but next time I'll use a 16-bit DAC for analog CV signal generation rather than the Arduino."

Spotted this one over on Ask.Audio where you'll find some additional words from creator Guenther.

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