Unipolar CVs range from 0 V to a positive maximum; bipolar CVs swing both positive and negative

Control voltages in modular synthesis come in two polarity flavors. Unipolar CVs range from 0 V upward — for example, 0–5 V for gates, 0–8 V for envelopes, or 0–10 V for some CV ranges. They only have one polarity: a note is “on” or “off”, a cutoff is “open to some degree”. Bipolar CVs swing both above and below zero — typically ±5 V or ±2.5 V — and are appropriate for modulation sources like LFOs (which need to sweep up and down from a center point) and pitch offsets. Misunderstanding polarity leads to common patching errors: a unipolar envelope into a bipolar FM input never goes below zero, so FM only brightens, never darkens. An attenuverter converts bipolar to unipolar (or vice versa) by offsetting or scaling.

Examples

LFO outputs ±5 V (bipolar) for vibrato centered around the base pitch. Gate outputs 0–5 V (unipolar) — only on or off. Envelope outputs 0–8 V (unipolar) — always positive. Plugging a unipolar envelope into a VCO FM input only pushes pitch up, never down.

Assessment

Explain why using a unipolar envelope as a vibrato source produces asymmetric vibrato (pitch only goes up). Describe how an offset module converts a bipolar LFO to a unipolar range.