Modulators

Amp

A simple voltage-controlled amplifier. One knob, two jacks: open the gate with CV, scale with LEVEL.

What is a Amp?

Basic VCA is the simplest voltage-controlled amplifier: one knob, two jacks. Audio goes in, audio comes out, and a CV signal opens and closes the gate in between. Linear-only response - no mode switch, no exponential curve - so the math stays transparent: the output is the input multiplied by CV (clamped to 0-10V) multiplied by LEVEL. The pedagogical reduction of the full VCA module: when students are ready for an exponential curve and a mode toggle, they swap in `ibp.vca` and the patching layout is identical. Member of the Basic series, intended as a first-touch teaching module for "CV controls volume."

In a patch

Patch an envelope (Basic AD's ENV is the natural pair) into CV, audio into IN, OUT to your output module - that is the canonical "voice in a box" patch and what every modular synth tutorial starts with. Patch an LFO into CV instead and you have tremolo: a slow CV rate (1-8 Hz) pulses the volume on a held tone. Leave CV unpatched and the LEVEL knob works as a manual volume fader, useful for setting a fixed gain on a noise source or quickly soloing one voice in a multi-voice patch. The lesson it teaches: 0V CV = silence, 10V CV = full open, anything in between scales linearly. When CV is patched, LEVEL becomes a final attenuator that scales the whole signal after the CV gate.

Inputs

IN (audio) — Audio input. Eurorack-standard +/-5V audio, but anything float-valued works (CV signals, sub-audio, etc). The VCA does not care what you patch in - it just multiplies. For voice patches, this is your VCO output (saw, square, sine). For noise patches, patch in a Noise module. For sub-bass swells, patch in an LFO at audio rate.
CV (cv) — Control voltage input, 0-10V unipolar (Eurorack envelope standard). 0V silences the audio entirely; 10V passes the audio at full level (scaled by LEVEL). Voltages above 10V or below 0V clamp to the boundary - useful for catching out-of-range modulators without surprising spikes. Most commonly fed by an envelope (Basic AD or ADSR ENV) or by an LFO with offset enabled. Without a cable patched, the VCA treats this as "always open" and falls back to LEVEL alone.

Outputs

OUT (audio) — The audio input scaled by CV (when patched) and by LEVEL (always). Patch into the L or R input of an Output module to hear it. For multi-voice patches, send into a Mixer8 channel. Range matches the input range - no internal saturation or clipping happens here, so feeding in +/-10V audio comes out at +/-10V (which most Output modules will then soft-clip).

Controls

LEVEL — Output level, 0-1 linear. With CV patched, this scales the post-CV signal: LEVEL=1 lets the CV control everything, LEVEL=0.5 cuts the whole output in half (useful for trimming a loud voice in a mix), LEVEL=0 silences the channel. Without CV patched, this acts as a manual volume fader: turn it up to pass audio through, turn it to 0 to mute. Default is 1 so a fresh Basic VCA passes audio at full level - drop it if your voice is louder than your mix needs.

Inspired by

Single-channel linear VCA stripped to one knob. Same CV semantics as ibp.vca's linear branch; mode toggle and exponential curve removed for first-touch students. When students transfer up to the full ibp.vca, the patch layout is identical.

Doepfer A-130
Mutable Instruments Veils

← Back to all modules