An open-source wavetable synthesizer exploring how far modern embedded audio can be pushed using only a handful of affordable components and carefully engineered software.
| Area | Status |
|---|---|
| Firmware | 🟢 Stable Foundation |
| Audio Engine | 🟢 Mature |
| MIDI | 🟢 Complete |
| User Interface | 🟢 Mature |
| Hardware | 🟡 Prototype |
| PCB | 🔵 Planned |
| Dual ESP32 FX | 🟡 Prototype |
- Introduction
- Engineering Vision
- Project Goals
- Design Philosophy
- Current Prototype
- Feature Overview
- Hardware Platform
- Software Architecture
- Development Timeline
- Future Development
- Future Hardware
- Open Engineering
- Repository Structure
- Acknowledgements
- License
WELLENBAD is not simply another DIY synthesizer.
It is an engineering study exploring how far modern embedded audio can be pushed using an affordable ESP32-S3 platform without sacrificing sound quality, usability or maintainability.
The objective is not merely to publish source code, but to document the complete engineering journey.
WELLENBAD is an open-source wavetable synthesizer built around the ESP32-S3.
Every hardware revision, firmware milestone and architectural decision is documented as part of the RealTimeAudioLab Engineering Archive.
- High-quality wavetable synthesis on affordable hardware
- Deterministic real-time DSP
- Modular firmware architecture
- Open engineering documentation
- Scalable hardware platform
- Educational reference for embedded audio development
How much synthesizer can be built using as little hardware, as few components and as little financial investment as possible?
Every design decision is evaluated according to:
- Sound quality
- CPU efficiency
- Low latency
- Real-time determinism
- Maintainability
- Simplicity
The ESP32-S3 combines floating-point processing, PSRAM support, USB, I²S and excellent cost efficiency, making it an ideal platform for modern embedded audio.
WELLENBAD intentionally demonstrates what can be achieved through efficient software engineering before adding hardware complexity.
The current engineering prototype is fully operational and serves as the primary development platform.
Implemented today:
- Polyphonic wavetable synthesis
- Morph engine
- OLED user interface
- MIDI
- User presets
- Sequencer
- Arpeggiator
- Floating-point DSP
- Dual wavetable oscillators
- Morph engine
- Sub oscillator
- Noise generator
- SD-card wavetable loading
- Polyphony
- Step sequencer
- Arpeggiator
- MIDI clock
- Compare / Undo
- User presets
- Floating-point DSP
- Soft limiter
- PCM5102A DAC
| Component | Device |
|---|---|
| MCU | ESP32-S3 |
| Flash | 16 MB |
| PSRAM | 8 MB |
| Display | SSD1309 OLED |
| DAC | PCM5102A |
| Storage | MicroSD |
| MIDI | DIN MIDI |
MIDI
│
▼
Voice Manager
│
▼
Oscillators
│
▼
Morph Engine
│
▼
Mixer
│
▼
Filter
│
▼
DSP Processing
│
▼
Limiter
│
▼
PCM5102A DAC
| Stage | Status |
|---|---|
| Project Start | ✅ |
| Audio Engine | ✅ |
| Morph Engine | ✅ |
| MIDI | ✅ |
| Sequencer | ✅ |
| User Presets | ✅ |
| Dual ESP32 | 🚧 |
- DC Blocker
- Soft Saturation
- Oversampling
- Improved Limiter
- Voice Priority
- Intelligent Voice Allocation
- Snapshot System
- Dirty-Flag Rendering
- Favorites
- Program History
- Swing
- Humanize
- Probability
- Parameter Locks
A future hardware generation will separate synthesis and effects processing onto two dedicated ESP32-S3 processors connected through synchronized Stereo I²S audio and a high-speed UART control link.
Unlike many repositories that publish only firmware, WELLENBAD documents:
- Firmware evolution
- Hardware revisions
- DSP concepts
- Design decisions
- Engineering notes
- Future concepts
- User and service documentation
The goal is to preserve not only the finished instrument, but also the complete engineering process.
doc/
firmware/
images/
schematic/
Historical inspiration:
- Wolfgang Palm
- PPG Wave
Open-source ecosystem:
- Marcel Licence
- Rolf Degen
- Mutable Instruments
- Craig Barnes
- Open Source Community
GNU General Public License v3
Engineering modern embedded audio systems through open development.