Host external plugins 🔌

CLAP effects

rusty-amp can host a third-party CLAP effect plugin as a stereo insert in the signal chain — placed after the cabinet/effects rack, just before the master bus.

Plugin hosting is enabled by default (it's in the pre-built binaries too), powered by the clack CLAP host bindings. If you want a minimal amp with no plugin dependencies or plugin-loading FFI, build with the feature turned off:

cargo run --release --no-default-features

Installing plugins

Put the plugin's .clap file (on macOS a .clap is a bundle directory) into one of the locations rusty-amp scans on startup:

Any directory listed in the CLAP_PATH environment variable is also searched (subdirectories included). Most plugin installers place the .clap in the right folder automatically.

Loading & configuring a plugin (V)

Press V to open the plugin browser, which (re)scans the locations above.

When a plugin with parameters is loaded you drop straight into the parameter editor:

The loaded plugin's name appears in the header (🔌) next to the amp and cabinet. Loading, clearing, and parameter edits all take effect live — the audio stream is never interrupted (swaps happen on a lock-free handoff, and the displaced plugin is freed off the audio thread).

CLAP limitations

• Headless — plugin GUIs are not opened; parameters are edited in the TUI (shown as raw numeric values).
• Effects only — instrument/synth plugins are not driven (there's no MIDI input).
• One insert slot, using the plugin's main mono/stereo audio ports (no sidechain or multi-out routing).
• Plugin state is not saved in rusty-amp presets, and is not recalled across restarts.

Audio Unit amps (macOS)

On macOS, rusty-amp can also host an Audio Unit (AU) effect — typically an amp-sim plugin such as a Marshall — as an amp-position override. This is different from the CLAP insert: rather than sitting at the end of the chain, a loaded AU replaces the built-in amp and cabinet. Your pre-amp pedal signal (gate → compressor → … → pre-EQ) is fed into the AU, and its stereo output continues through the post-cab rack (parametric EQ → flanger → chorus → delay → reverb) and the master bus. That's the correct routing for amp sims, which bring their own cabinet.

AU hosting uses the CoreAudio/AudioToolbox frameworks, so it is macOS-only and enabled by default in the macOS builds. It compiles to nothing on Linux/Windows. To build a macOS binary without it:

cargo run --release --no-default-features --features clap

rusty-amp lists every effect Audio Unit registered with the system — both Effect (aufx) and Music Effect (aumf) component types, the same units your DAW sees. Installing an AU is handled by its own installer (into /Library/Audio/Plug-Ins/Components/ or the per-user equivalent under ~/Library/…); rusty-amp discovers them automatically on open — there's no folder to manage.

Loading & configuring an AU amp (U)

Press U to open the AU amp browser, which enumerates the installed Audio Units.

When an AU with parameters is loaded you drop straight into the parameter editor (identical controls to the CLAP editor):

Parameter values are shown the way the plugin describes them: enum/switch parameters read as their names (e.g. Bright / Normal), and unit-bearing parameters carry a suffix (-6.0 dB, 2.50 kHz, 50 %, 12.0 ms, On/Off). Continuous params fall back to a plain number. Adjusting a switch/list param snaps one entry at a time.

Loading an AU makes it the active amp immediately: the built-in amp is bypassed, the header shows AU: NAME in place of the amp model, and the built-in tone-stack knobs and AMP selector dim to signal they no longer affect the sound. Press Z to A/B between the loaded AU and the built-in amp live — no reload.

Cab pairing (C)

By default the AU is treated as a full amp + cab — it supplies its own cabinet, so the built-in cab (and any loaded IR) is bypassed and the cabinet/mic panel reads PLUGIN CAB. If your AU is an amp-only model that expects a separate cab, press C in the AU browser to switch to amp-only: the AU's output is then run through rusty-amp's built-in cabinet (or your loaded IR), and the mic knobs / IR loader come back to life. The AU modal's status line shows the current mode (plugin cab vs built-in cab).

Latency

rusty-amp reads the AU's reported processing latency and shows it in the AU modal status line (e.g. active: NAME 5.2 ms · plugin cab). While an AU is loaded, the built-in amp path is delayed by the same amount, so switching built-in↔AU with Z stays time-coherent and recordings line up. (Processing latency itself can't be removed from a live monitoring signal — this only keeps the two amp sources aligned with each other.)

AU limitations

• macOS only — the feature is inert on Linux/Windows.
• Amp + cab by default — the AU supplies its own cabinet and the built-in cab/IR is bypassed. Press C for amp-only mode to keep the built-in cab (or your loaded IR) in the path instead.
• Headless — the AU's GUI is not opened; parameters are edited in the TUI (with unit/enum-aware value display).
• Effect components only (aufx / aumf) using the main stereo (or mono) ports; instruments aren't driven.
• Parameters are driven one-way — edits from the TUI reach the plugin, but changes the AU makes internally (its own presets/automation) aren't reflected back, and the AU's own presets can't be loaded.
• AU state is not saved in rusty-amp presets, and is not recalled across restarts.