TYPE-2 Autonomous Polyphonic Synthesizer

Version: v1.6.0

Author: Alexandre Esnard

The TYPE-2 is a microcontroller-based hybrid polyphonic synthesizer. Engineered entirely around a highly optimized DSP core, it leverages fast polynomial saturation, a dual-rate processing architecture, and analog-modeled filters to deliver a heavy, studio-quality audio signal flow.

Designed with accessibility in mind, it is highly affordable (around €35 in total components) and features a near-zero difficulty build process requiring minimal wiring.

Hardware BOM

• ESP32-S3 Microcontroller (16MB Flash, PSRAM strictly required)

• PCM5102A I2S DAC Module

• SSD1306 128x64 OLED Display

• KY-040 Rotary Encoder

• 1x Tactile Navigation Button

• 2x MPR121 I2C Capacitive Touch Sensors

• Copper tape (for creating capacitive touch keys)

Core Features

• Hybrid DSP Engine: Fast polynomial saturation and dual-rate architecture.

• Signal Chain: Factorized 24dB/Oct Trapezoidal SVF Filter, Tube Overdrive, and Studio Digital Delay.

• User Interface: Cylindrical rotary menu interface and responsive topological grid visualization.

• Connectivity: Composite USB Device (Native USB MIDI Out + USB PCM Audio Stream) for direct DAW integration.

Repository Structure

• enclosure/ : 3D models and CAD files for the synthesizer casing.

• firmware/ : Contains the main TYPE2.ino firmware file and the type2_audio_bridge.py script for USB Audio streaming.

• hardware/ : Contains the KiCad project files (.kicad_pro, .kicad_sch, .kicad_pcb), the schematic/wiring diagram, and a ready-to-manufacture Type2_v2_Gerber.zip file.

Setup & Installation

1. IDE Setup: Install the Arduino IDE or PlatformIO with ESP32 board support.

2. Compiler Settings: To ensure the DSP engine, display tasks, and USB native features run properly, configure your IDE with the following exact parameters:

   • USB Mode: USB-OTG (TinyUSB) or Hardware CDC and JTAG

   • USB CDC On Boot: Enabled

   • CPU Frequency: 240MHz (WiFi)

   • Flash Mode: QIO 80MHz

   • Flash Size: 16MB (128Mb)

   • Partition Scheme: 16M Flash (3MB APP/9.9MB FATFS)

   • PSRAM: OPI PSRAM

   • Upload Speed: 115200

3. Libraries: Install Adafruit GFX, Adafruit SSD1306, and Adafruit MPR121.

4. Wiring: Refer to the wiring_diagram.md in the hardware/ folder to route the I2S, I2C, and GPIO connections correctly.

5. USB Audio Bridge (Optional): To stream audio directly over USB, run the type2_audio_bridge.py script located in the firmware/ folder on your host machine.

PCB Design

This project is proudly supported by PCBWay, who generously provided the manufacturing for the TYPE-2 printed circuit boards. Their service offers exceptional quality, which is crucial for audio applications where proper ground planes, trace routing, and impedance control directly impact the final sound quality.

The silkscreen precision on the touch pads and the fast turnaround times have been instrumental in the prototyping and finalization of this synthesizer.

If you want to build your own TYPE-2, you can use the production-ready Type2_v2_Gerber.zip file located in the hardware/ folder. I highly recommend ordering your boards from PCBWay for guaranteed compatibility and professional finish.

Hardware BOM

• ESP32-S3 Microcontroller Board (ESP32-S3-DevKitC-1 form factor, 16MB Flash, OPI PSRAM required)
• PCM5102A I2S DAC Module
• SSD1306 128x64 I2C OLED Display
• KY-040 Rotary Encoder
• 1x Tactile Navigation Button
• 2x MPR121 I2C Capacitive Touch Sensors
• Custom TYPE-2 Motherboard PCB (or breadboard + copper tape)

CRITICAL ESP32-S3 PINOUT & FORM FACTOR NOTICE:
The custom PCB footprint is specifically routed for the standard ESP32-S3-DevKitC-1 form factor featuring 44 pins (2x22 pin headers, 2.54mm pitch) and an onboard 16MB Flash / 8MB OPI PSRAM (e.g., ESP32-S3-WROOM-1 / N16R8 module).
Do not use 38-pin or compact 30-pin ESP32-S3 boards, as their power and GPIO pinouts will not align with the PCB socket and will cause short circuits. Before soldering, always verify your board's pinout against hardware/wiring_diagram.md and the KiCad schematic hardware/Type2_v2.kicad_sch.

Roadmap

• Core 7-voice polyphonic DSP engine implementation

• Tube overdrive, analog slop, and delay effects

• Real-time topological grid UI and hierarchical menu

• Advanced firmware optimization

• Improved menu navigation

• Manage the creation of presets from a dedicated menu

• External MIDI communication (USB/Serial)

• Custom PCB design

• Direct USB PCM Audio streaming (Python Bridge)

• ESP32 Bluetooth communication integration

• Battery management and portable power components integration

• Enclosure design and manufacturing

Links & Contact

• GitHub Repository

• YouTube Channel

• LinkedIn Profile

• Reddit Development Log

• Instructables

• alxdreee.esn@gmail.com

Support the Project | Donation Page

This project is 100% open-source and developed entirely on my own in my spare time. If you find it useful or like what I'm doing, you can support its development here!

Buy Me a Coffee

License & Copyright

This project is an open-source initiative developed for the benefit of the maker and synthesizer community.

• Community Use: You are entirely free to study, modify, and build upon this code for your personal projects.

• Commercial Restriction: The commercial resale of this project, its code, or any hardware derivatives based directly upon this architecture is strictly prohibited.

• Patent Restriction: No patents, trademarks, or restrictive intellectual property rights may be filed on this work or its derivatives.