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Why this exists

Every "pro mic" voice you hear on a stream or podcast is a chain of plugins — a gate, a compressor, an EQ, a de-esser, a noise suppressor. Getting that normally means running a DAW, fighting ASIO loopback, or paying a monthly fee for a voice changer with a fixed effect library.

VST-Applier is the small missing program: it hosts your VST plugins (the same ones you'd use in a DAW) on your microphone in real time and pumps the result into a virtual audio cable. No DAW. No subscription. No re-buying effects you already own.

How it compares

To be fair: if you want a full virtual mixing desk with buses and per-app routing, use VoiceMeeter Potato — it is excellent at that. VST-Applier is deliberately narrower: one microphone, one plugin chain, one output, nothing to configure.

Features

• Real-time VST2 + VST3 chain on your mic, typically ~10–100 ms round trip depending on buffer and devices.
• Live chain editing — add, remove, reorder, enable/disable plugins while audio is running. No cut, no restart.
• 21 plugins bundled — RNNoise (mono/stereo), DeepFilterNet, Alt Denoiser, Bertom Denoiser, DeeGate, TDR Nova, and the REAPER ReaPlugs suite (ReaEQ, ReaGate, ReaComp, …). Point it at any VST folder to scan more.
• Settings preserved — every plugin keeps its knob positions across bypass, reorder and restarts. Your chain auto-saves on every exit, including during updates.
• Profiles — save and load named setups ("podcast", "game chat", "noisy room"); the active one restores at launch.
• Safe engine — a misbehaving plugin is contained by Windows SEH and reported as an error instead of taking the app down. Audio threads are panic-isolated, with a lock-free ring buffer, dropout counter, and honest measured latency / sample rate / buffer readout.
• Quality of life — system tray with single-instance wake, start-with-Windows, Dark / Light / System themes, folder picker for your plugin directory.
• Self-updating — checks GitHub Releases and stages the update in place.

Install

Requires Windows 10 or 11 (x64). No account, no signup, nothing to configure.

1. Download VST-Applier-Setup-vX.Y.Z.exe and run it. The wizard bundles the two native host DLLs and the plugin pack, and can install the VB-CABLE virtual audio driver for you (recommended — it is skipped if you already have it; needs one reboot).
2. Open VST-Applier and set input = your microphone, output = CABLE Input (VB-Audio Virtual Cable).
3. Add plugins from the PLUGINS panel, then press START.
4. In Discord / Zoom / OBS / Teams, set your microphone to CABLE Output (VB-Audio Virtual Cable).

A portable zip (VST-Applier-vX.Y.Z-win64.zip) is attached to every release as well — it is the same payload the in-app updater uses.

Windows SmartScreen will warn you on first run. The installer is not code-signed (certificates cost money and this is a free project), so Windows reports an unrecognised app — click More info → Run anyway. The full source is in this repository and every release is built from it.

Screenshots

How it works

mic ──► WASAPI capture ──► mono ──► VST2/VST3 chain (48 kHz) ──► resample ──► VB-CABLE ──► Discord/Zoom/OBS

• Capture and render run on separate streams joined by a lock-free ring buffer with an occupancy servo, so microphone and cable clock drift can never starve or flood the audio.
• The chain is one native plugin instance per slot, hosted through Vst2HostNative.dll / Vst3HostNative.dll.
• Latency is set by the buffer (128–4096 samples; 1024 is the default → snappy UI, stable audio).

FAQ

Does this count as a voice changer / will it get me banned? It is a microphone processor. It does not inject into games, hook processes, or touch anti-cheat. It presents itself to your apps as a normal audio device.

Is it really free? Yes — MIT licensed, no account, no telemetry, no "pro" tier. Bundled plugins keep their own licenses.

Can I use plugins I already own? Yes. Point the plugin folder chip at your VST folder and hit SCAN. Anything that works in a DAW should host here.

Why not just use Voicemod? Voicemod gives you its effect library on a subscription. This gives you any VST you want, forever, for free.

Why not just use a DAW? You can — if you enjoy ASIO loopback, aggregate devices, and keeping a DAW open forever. This is one window and a START button.

Latency is too high / it crackles. Crackles mean the buffer is too small for your CPU; latency too high means it is too big. Move the buffer slider and watch the measured readout in the status bar.

Does it work with OBS / Discord / Zoom / Teams / Google Meet? Yes — any app that lets you pick an input device. That is the whole point of routing through a virtual cable.

Tips

• Lowest latency: drop the buffer; if you hear crackles, raise it.
• Click the plugins-folder chip (bottom-right) to point at any VST folder, then hit SCAN.
• The bottom status bar shows buffer, sample rates and measured latency; hover it for full diagnostics.
• Updates: SETTINGS → Check now. Failures are logged to %APPDATA%\VstApplier\pending\install.log.

Building from source

Requirements: Rust stable (MSVC toolchain) with cargo — that's it. Everything, including the two VST host DLLs, builds from this workspace; there is no C/C++ source in the repo.

cargo build --release
# -> target\release\vst-applier.exe
#    target\release\Vst2HostNative.dll
#    target\release\Vst3HostNative.dll

Self-checks

cargo run -p audio-engine --example chain_hot_add   # live chain edits on a running route
cargo run -p app-state    --example profile_roundtrip
cargo test -p vst2-host-dll -p vst3-host-dll        # SEH guard: faults and panics are caught

Third-party

• VB-CABLE virtual audio driver by VB-Audio — bundleable installer, donationware.
• microseh (MIT) — supplies the Windows SEH hardware-exception guard (a tiny __try/__except stub compiled at build time) that lets the host DLLs report a faulting plugin as an error instead of crashing — the same protection the former C++ host implemented by hand.
• Bundled plugins keep their own licenses: REAPER ReaPlugs (Cockos), RNNoise builds (Xiph/werman), DeepFilterNet, Alt Denoiser, Bertom Denoiser, DeeGate, TDR Nova (Tokyo Dawn Labs).

Legacy

The original C# implementation (WinForms app + earlier native hosts) lives on the csharp-legacy branch and in the v0.1–v0.3 tags.

License

MIT — see LICENSE.

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