A FOSS TB-303-style acid bassline synthesizer plugin. VST3 + CLAP + standalone.
Built with Rust, nih-plug, and egui.
Full-quality MP4: assets/demo.mp4. Static screenshot: assets/screenshot.png.
Hear it in your browser — 320 kbps demo.
One-click downloads for the latest release. Each archive contains VST3, CLAP, and standalone binaries plus an install script.
| Platform | Download |
|---|---|
| Windows (x86_64) | squelchbox-windows-x86_64.zip |
| macOS (Apple Silicon) | squelchbox-macos-arm64.zip |
| macOS (Intel) | squelchbox-macos-x86_64.zip |
| Linux (x86_64) | squelchbox-linux-x86_64.tar.gz |
| Checksums | SHA256SUMS.txt |
See install instructions for your platform below. Arch Linux users: paru -S squelchbox (see AUR).
- Oscillator -- bandlimited saw + square (BLIT/polyBLEP), drift LFO for analog warmth
- 3-pole diode ladder filter -- self-oscillating, with 2x oversampling via half-band polyphase
- Envelopes -- authentic TB-303 VEG (gate-driven amp), one-shot filter (adjustable curve), accent envelope with 300 ms RC decay and charge accumulation
- 16-step sequencer -- per-step pitch/accent/slide/rest, pattern length 1-16, swing, 4-bank pattern memory
- Sync modes -- Internal (free-run), Host (DAW transport slave), MIDI (keyboard only)
- FX chain -- Diode distortion, tempo-synced delay (analog/clean), Schroeder reverb, loudness comp, brickwall limiter
- Slide/glide -- portamento between legato steps, authentic 303 slide behavior
- Computer keyboard -- chromatic note input, step editing (during playback), click-drag draw, tap tempo, pattern randomizer
- MIDI export -- dump patterns as .mid files
After grabbing the archive for your platform from the Download section:
tar xzf squelchbox-linux-x86_64.tar.gz
./install.sh
# Rescan plugins in your DAWInstalls to ~/.vst3/, ~/.clap/, and ~/.local/bin/.
- Double-click the downloaded
.zipto extract it. - Right-click
install.sh→ Open With → Terminal (or drag it into a Terminal window). - Rescan plugins in your DAW.
Installs to ~/Library/Audio/Plug-Ins/VST3/, ~/Library/Audio/Plug-Ins/CLAP/, and ~/.local/bin/.
The binaries are unsigned. install.sh auto-removes the com.apple.quarantine xattr from everything it writes so Gatekeeper won't block your DAW from scanning the plugin. If the DAW still refuses, right-click the .vst3 bundle in ~/Library/Audio/Plug-Ins/VST3/ and choose Open.
Standalone note: Use the included squelchbox-macos.sh launcher instead of running squelchbox-standalone directly. CoreAudio delivers variable-sized buffers that can exceed the configured size, causing a panic in nih-plug's CPAL backend. The launcher passes --period-size 4096 to accommodate this. See nih-plug#266.
Extract the .zip and run install.bat (may need Administrator for the VST3/CLAP paths).
Installs VST3 to %CommonProgramFiles%\VST3\, CLAP to %CommonProgramFiles%\CLAP\, and standalone to %LocalAppData%\SquelchBox\.
Standalone note: Use SquelchBox.bat (not squelchbox-standalone.exe directly). WASAPI in shared mode delivers buffers in the device's native period (often 1056-1266 samples on Windows 11), exceeding nih-plug's default 512-sample buffer. The launcher passes --period-size 2048 to avoid this.
paru -S squelchbox # or yay, makepkg, etc.Installs VST3 and CLAP system-wide to /usr/lib/vst3/ and /usr/lib/clap/, standalone to /usr/bin/squelchbox.
Each release includes a SHA256SUMS.txt. After downloading:
sha256sum -c SHA256SUMS.txtRequires Rust stable 1.75+ (or nightly).
# Check / test
cargo check
cargo test
# Bundle VST3 + CLAP
cargo xtask bundle squelchbox --release
# Install (Linux)
rm -rf ~/.vst3/squelchbox.vst3
cp -r target/bundled/squelchbox.vst3 ~/.vst3/
cp -f target/bundled/squelchbox.clap ~/.clap/
# Standalone (Linux — match your PipeWire/JACK sample rate)
cargo run --release -- --sample-rate 44100 --period-size 512src/
lib.rs -- crate root
plugin.rs -- nih-plug Plugin impl, process loop
params.rs -- parameter definitions (knobs, toggles, FX)
kbd.rs -- keyboard/MIDI event queue (GUI <-> audio)
main.rs -- standalone entry point
dsp/
oscillator.rs -- bandlimited saw + square
envelope.rs -- authentic 303 VEG, filter env, accent env (300ms RC)
filter_diode.rs -- 3-pole diode ladder (bilinear transform)
oversampler.rs -- 2x half-band polyphase up/downsample
voice.rs -- monophonic voice: osc + filter + envelopes
fx/ -- distortion, delay, reverb, limiter, FxChain
sequencer/
clock.rs -- tempo clock with swing
pattern.rs -- 16-step pattern + 4-slot bank
runtime.rs -- sequencer state machine
ui/
mod.rs -- editor entry point (create())
ids.rs -- centralized egui ID registry
palette.rs -- colors + layout constants
widgets.rs -- param knob, button painters
keyboard.rs -- keyboard input, pattern persistence
panels/ -- faceplate, band1, band2, fx_dist, fx_time, toast
lower/ -- left strip, pitch row, step grid, transpose, right strip
util/
paths.rs -- XDG data/config/preset directories
midi_export.rs -- pattern-to-MIDI file export
| Crate | Purpose |
|---|---|
| nih-plug | Plugin framework (VST3/CLAP/standalone) |
| nih_plug_egui | egui integration for plugin GUIs |
| parking_lot | Fast mutexes for audio/GUI sync |
| rtrb | Lock-free SPSC ring buffer |
| serde + serde_json | Pattern bank persistence |
| tracing | Structured logging |
GPL-3.0-or-later -- required by nih-plug's license.