suppressor

Zero-latency, frequency-split noise suppressor for guitar DI — built for high-gain amp-sim and reamping chains. It sits on the raw DI before the amp sim, strips pickup-borne hiss/buzz/EMI between notes, and leaves the guitar body alone. Formats: VST3 and CLAP (Windows, macOS, Linux).

What it does

The core is a causal, sample-domain dynamic low-pass:

• the input is split by a fourth-order Linkwitz–Riley-style crossover;
• the low branch always passes (body, fundamentals, sustain);
• the high branch is gated by an envelope detector that listens to the high branch itself — bass energy can't reopen the noise branch, pick attack and string harmonics can;
• the gate opens in 10 µs, holds through waveform zero-crossings, and closes on a smooth exponential release.

The result: noise between notes disappears in the band where hiss/buzz lives, while low mids and body pass untouched and pick transients survive intact. Zero reported latency in the default mode; negligible CPU (four biquads plus an envelope per channel).

Controls

Section	Controls
Core	Strength (crossover 8 kHz → 1.4 kHz), Threshold, Release (2–30 ms, exponential)
Gate	Reduction / Tight Gate mode, Depth floor, Hysteresis, Hold, Adaptive Release
Detection	Transient Cue, internal/external detector source, 0/1/2 ms lookahead
Hum Removal	Learn-and-lock resonant dips on the 50/60 Hz family, strength, harmonic count
Multiband	Optional 4/6-band learned-threshold mode (advanced; one-split is the default)
Output	Delta (removed-signal) audition, output gain, detector/GR metering

Building

Requirements: CMake ≥ 3.22, a C++17 compiler, Ninja (recommended). JUCE and the CLAP wrapper are fetched automatically (pinned versions).

cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build --target Suppressor_VST3 Suppressor_CLAP Suppressor_Standalone

Outputs land in build/Source/Suppressor_artefacts/Release/{VST3,CLAP,Standalone}.

Unit tests

cmake -S . -B build-tests -G Ninja -DSUPPRESSOR_BUILD_PLUGIN=OFF -DSUPPRESSOR_BUILD_TESTS=ON
cmake --build build-tests && ctest --test-dir build-tests --output-on-failure

CI

.github/workflows/ci.yml gates every push/PR on:

1. DSP unit tests on Windows, macOS, and Linux;
2. VST3 + CLAP builds on all three platforms (macOS universal);
3. validation with pluginval (VST3) and clap-validator (CLAP);
4. per-OS artifact packaging. Tags matching v* publish a GitHub release.

Design documentation

See docs/DESIGN.md for the full DSP specification: topology, parameter laws, timing, and the rationale behind every improvement over a plain one-split gate.

License

GPL-3.0-or-later (see LICENSE). This project is built with JUCE (also available under the GPL); a commercial JUCE licence would permit proprietary relicensing. CLAP is MIT-licensed.