DIY Arduino-Based Hardware Chiptune Synthesizer

Youtube user GumpherDM3 shared this video demo of a DIY MIDI-capable, Arduino-controlled monophonic semi-modular analog synthesizer, the Guenther Chiptune.

It’s not a traditional chiptune instrument, but an analog synth with arpeggiator, tailored to creating ‘video game-esque’ sounds.

Here’s what he has to say about the Guenther Chiptune:

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.

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