Mixing & Output

Audio In

External audio into the rack - mics, hardware synths, and audio interfaces at Eurorack levels.

What is a Audio In?

An audio-input module is the door that lets the outside world into a modular synthesizer. By default a rack is a closed system: every voltage in it was generated inside the rack and goes back out through the Output. An external input module breaks that loop. It takes a signal from outside - a microphone, an electric guitar, a hardware synth, an audio interface, the line output of a record player - and turns it into a Eurorack-level voltage that any other module can patch.

The conversion matters. Line-level audio is small (a fraction of a volt), instrument-level smaller still, microphone level smaller again - all of them well below the ±5V peak-to-peak that modular synths run at. So an external-input module always includes a gain stage to lift the incoming signal up to rack level. Without that boost, your filter would barely notice the input; with it, your guitar sits at the same voltage as a VCO and behaves identically.

Once you have an audio-input module, every effect in the rack is suddenly an effect for your *external instrument*. A guitar becomes a guitar through a modular - its dry signal feeding delays, reverbs, filters controlled by LFOs and envelopes. A drum machine becomes a drum machine inside a modular, with each hit feeding a Compare to extract gates, or a VCA to be ducked rhythmically. The rack stops being an island.

Our Audio In

Webrack's Audio In is 10 HP and exposes the browser's getUserMedia API: pick any audio input device the operating system reports - built-in mic, an audio interface, a USB synth, a guitar through a Scarlett - from the dropdown, click Connect, and the device appears at the L / R / M outputs at modular ±5V levels.

We disable every browser-side audio process before opening the stream: echoCancellation, noiseSuppression, and autoGainControl are all forced off. That single decision is the difference between a usable hybrid input (clean line-level pass-through) and a phone-call-quality compressor that ruins the music. Your guitar sounds like your guitar.

Audio In and Stream In use *separate* worklet inputs, so you can run a microphone and a browser tab capture simultaneously - sing into Audio In while a YouTube backing track flows through Stream In, both feeding the same mixer. Latency is one audio block, about 3ms - low enough to play in real time without a perceptible lag.

In a patch

External audio almost always feeds an effect chain. The classic move is Audio In -> Filter -> Reverb -> Output, with an LFO slowly sweeping the filter cutoff so a static guitar tone becomes an evolving texture. Swap the filter for a Ladder for a warmer color, or drop a Distortion before the reverb for grit.

For hybrid setups, mix external and internal sources in a Stereo Mixer. Pan a hardware synth left, a Webrack VCO right, and you are layering hardware and software in the same bus. The two voices share the same final Output and effects.

Use the audio input as a *modulation source*, not just a sound source. Patch it through an envelope follower (a slow Filter plus a rectifier-style chain) and the loudness of your guitar suddenly modulates the cutoff of a synth voice. The rack becomes performable from outside.

Outputs

L (audio) — Left channel from the selected input device, at Eurorack +/-5V. Outputs silence until you click Connect on the panel.
R (audio) — Right channel. Carries the same signal as L for mono inputs (the browser duplicates the channel).
M (audio) — Sum (L+R)/2. Convenient when downstream effects only need one channel.

Controls

Gain — Input gain, 0-2x. Boost quiet sources (mics, passive pickups) or attenuate hot ones. Watch the Stereo Meter to avoid clipping.
Mute — Silences the output without disconnecting from the device. Faster than re-arming the connection.

Inspired by

The browser equivalent of a classic external-audio module: take any line-level or instrument-level signal from outside the rack, scale it up to modular range, and hand it to the patch as a regular audio jack.

Doepfer A-119 External Input
Intellijel Audio I/O
Befaco Instrument Interface

← Back to all modules