Loopbacker

Virtual audio loopback + broadcast voice processing for macOS.

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Loopbacker creates a virtual audio device on macOS that captures audio from any app and makes it available as a mic input. Route desktop audio into Discord, OBS, Zoom, or any recording app. It also has a full audio effects chain for broadcast voice processing, and a soundboard for playing audio clips through the virtual device.

Features

Audio Routing

• Virtual stereo loopback device (48kHz / 32-bit float)
• Route any input device to the virtual output
• Monitor output (hear yourself through speakers)
• Per-channel routing with visual cable connections
• 8 independent virtual loopback devices
• Scenes system for saving/loading routing configs

Effects Chain (9 real-time DSP effects, all processed on the audio thread)

• Noise Gate -- soft expander with configurable threshold
• 5-band Parametric EQ -- draggable frequency response curve, highpass/peaking/shelf filters
• Compressor -- linked stereo detection, adjustable ratio/threshold/makeup
• De-Esser -- bandpass sidechain targeting 4-8kHz sibilance
• Chorus -- modulated delay line with stereo LFO
• Pitch Shift -- -12 to +12 semitones, dual-head overlap-add
• Reverb -- Freeverb algorithm (8 comb filters + 4 allpass diffusers)
• Delay -- echo with feedback + soft-clip safety
• Limiter -- brick-wall peak limiter, always last in chain

12 factory presets: Broadcast Masculine Voice, Podcast Clean, Radio Announcer, Chipmunk, Deep Voice, Robot, Telephone, Cathedral, Dreamy, Space Station, and more. Save your own presets, import/export as JSON to share with others.

The EQ settings match jtrv's EasyEffects Masculine NPR Voice preset -- the same signal chain used by podcasters and streamers on Linux, ported to native macOS with zero dependencies.

Soundboard

• Play audio files (MP3, WAV, M4A, AIFF, FLAC, CAF) through the virtual device
• Add individual files or scan an entire folder
• Drag and drop audio files onto the grid
• Multiple simultaneous sounds (CoreAudio mixes them on the device)
• Global volume control
• Sounds appear in Discord/Zoom/OBS as if they're your mic

UI

• Three tabs: Routing, Effects, Soundboard
• Snaking pipeline view with animated cable connections
• Adaptive light/dark theme with in-app toggle
• Menu bar quick access panel

How it works

Mic / App Output                        Discord / OBS / Zoom
       |                                       ^
       | capture                               | reads as mic input
       v                                       |
   [ Effects Chain ]                           |
   Gate > EQ > Comp > DeEss >                 |
   Chorus > Pitch > Reverb > Delay > Limiter  |
       |                                       |
       v                                       |
   +---+---------------------------------------+---+
   |              Lock-free Ring Buffer             |
   +------------------------------------------------+
                  Loopbacker Virtual Device

A CoreAudio HAL plugin provides the virtual device. The SwiftUI app handles routing, effects processing, and driver installation. All DSP runs on the real-time audio thread with no allocations or locks.

Install

From source

Requires Xcode command-line tools and CMake (brew install cmake).

make all          # Build driver + app
make install      # Install driver (sudo) + app to /Applications

From release

Download from Releases.

Uninstall

make uninstall    # Remove driver + app

Usage

1. Open Loopbacker.app and click Install Driver (requires admin).
2. Add your microphone as a source in the Routing tab.
3. Connect source channels to output channels by clicking the connector dots.
4. In your chat/recording app, select Loopbacker as the input device.
5. Switch to the Effects tab to enable broadcast voice processing.
6. Switch to the Soundboard tab to play audio clips through the virtual device.

Project structure

loopbacker/
├── Driver/          CoreAudio HAL plugin (C++17, CMake)
│   └── src/         Lock-free ring buffer, driver vtable, device management
├── App/             SwiftUI companion app (Swift 5.9)
│   └── Sources/
│       ├── Models/      AudioSource, AudioRoute, EffectsPreset, SoundboardItem
│       ├── Services/    AudioRouter, AudioEffectsChain, SoundboardPlayer
│       └── Views/       ContentView, EffectsView, SoundboardView, ...
├── scripts/         Install/uninstall helpers
└── docs/            Architecture docs

Requirements

• macOS 14+ (Sonoma or later)
• Apple Silicon or Intel (universal binary)
• CMake 3.20+

License

FSL-1.1-MIT -- free to use for any non-competing purpose, converts to MIT after 2 years.