An attenuverter scales a signal from full positive through zero to full inverted with one knob

An attenuverter is a single bipolar control that both attenuates (reduces gain) and inverts (flips polarity) — its name is a portmanteau of ‘attenuator’ and ‘inverter’. Turned fully clockwise it passes the signal at full positive amplitude (unity); at the centre (12 o’clock) the output is zero regardless of input; turned fully counterclockwise it passes the signal inverted at full amplitude (negative unity). Positions between centre and clockwise pass a reduced positive signal; positions between centre and counterclockwise pass a reduced inverted signal. This lets one knob replace two separate controls — an attenuator plus a polarity switch — and set both how much a modulation source affects a destination and in which direction, enabling smooth, performable transitions from normal to inverted modulation. Attenuverters are ubiquitous in modular systems for shaping modulation depth and polarity, usually sitting as a knob beside a CV input; recognising them removes a common barrier to reading patch diagrams.

Examples

Bipolar LFO (±5 V) → attenuverter → VCF cutoff CV: at full CW the LFO opens the filter on its peaks; at 12 o’clock there is no modulation; at full CCW the LFO is inverted so the filter closes on its peaks; at half CW it modulates positively at half depth. A small CCW setting applies a little inverted envelope to a VCO for pitch-tracking compensation.

Assessment

A bipolar LFO outputs ±5 V (or a 0–5 V triangle): describe the attenuverter’s output at full CW, 12 o’clock, half CW, and full CCW. Distinguish an attenuverter from a plain attenuator, and give a patch situation where you specifically need the inverted setting.