The organic response of Vactrols.

Ever since the low pass gate was invented by Don Buchla for his 200 series instruments in the early 1970s, low pass gates have been heralded for their ability to add a lifelike and organic response to modular synth patches. They work by applying an envelope to a low pass filter with its 0-voltage cutoff frequency way below audible range, so when the envelope is down, the 'gate' is closed. As a note decays, its high frequencies die soonest – just like most acoustic sounds.

The use of a vactrol, or light-based sensor, like those used in optical compressors, lend this design even more lifelike and musical response. Refined and expanded by Doepfer, and now available as an officially licensed expansion for Softube Modular, the Doepfer A-101-2 Vactrol LPG adds some biology to your patches.

In short

• Made for Modular, Softube's Eurorack platform. Learn more about Modular

• Vactrol control of a 12 dB low pass filter and a voltage controlled amplifier

• Switch between three different sets of vactrols — slow, medium and fast

• Auxiliary control of output mode (Low Pass, LPG or VCA mode) via the G1 and G2 inputs