Digital Synth VRA8-Px for Arduino Uno

Made by ISGK Instruments

• https://github.com/risgk/digital-synth-vra8-p/tree/vra8-px-v2
• http://risgk.github.io/

Concept

• 3 Voice Paraphonic Synthesizer for Arduino Uno
• A Variant of Digital Synth VRA8-P

Features

• 3 Voice Paraphonic Synthesizer (Pseudo Polyphonic Synthesizer), MIDI Sound Module
• Serial MIDI In (38400 bps), PWM Audio Out (Pin 6), PWM Rate: 62500 Hz
• Sampling Rate: 15625 Hz, Bit Depth: 8 bits

Demo Audio

• https://soundcloud.com/risgk/sets/digital-synth-vra8-px

Notes

• Exhibited in Ogaki Mini Maker Faire 2016

• Exhibited in Maker Faire Tokyo 2017, Analog Synth Builders' Summit 17

VRA8 Series

• Digital Synth VRA8-P https://www.instructables.com/id/Digital-Synth-VRA8-P-for-Arduino-Uno/
• Digital Synth VRA8-M https://www.instructables.com/id/Digital-Synth-VRA8-M-for-Arduino-Uno/

Step 1: Wiring

Required Hardware

• A1: Arduino Uno
• U1: 3.5 mm Audio Jack
• R1: 150 ohm Resistor
  • or 140 ~ 160 ohm Resistor (e.g. 100 + 47, 100 + 27 + 27)
• R2: 100 ohm Resistor
• C1: 100 nF Capacitor
• Wires

Wiring

• See the image

Step 2: Software Installation

1. Download Source code and extract it.
   
   • From https://github.com/risgk/digital-synth-vra8-p/tree/vra8-px-v2
2. Download Hairless MIDI<->Serial Bridge and extract it.
   
   • From http://projectgus.github.io/hairless-midiserial/
3. Download loopMIDI and install it.
   
   • From http://www.tobias-erichsen.de/software/loopmidi.html

Step 3: Start Synthesizer

Explanation for Windows

1. Write DigitalSynthVRA8Px.ino to Arduino Uno and quit Arduino IDE.
   • CAUTION: Use Arduino IDE 1.8.1 or later.
2. Start loopMIDI.
3. Start hairless-midiserial.exe (Hairless MIDI<->Serial Bridge).
   • Set [File] > [Preferences] > [Baud rate] to 38400 bps.
   • Select Arduino Uno (COM*) on Serial Port.
   • Select loopMIDI Port on MIDI In.
4. Open vra8-px-ctrl.html (VRA8-Px CTRL) with Google Chrome.
   • Select loopMIDI Port on MIDI OUT.
   • Select a MIDI controller on MIDI IN (if you have it).
5. Click (or touch) the Software Keyboard, and you can hear the sound.

CAUTION

• Click sounds may occur when you connect the audio out to an amp/a speaker or reset the board
• Click sounds may occur when you change the controllers (especially AMP EG and FILTER CUTOFF)
• Low FILTER CUTOFF with high FILTER RESO can damage the speakers
• The Arduino PWM audio output is a unipolar LINE OUT
  • Please connect this to a power amp/a headphone amp (not to a speaker/a headphone directly)