Dual Gate

Dual Gate

is a very simple module that features the emulation of two vactrol-based Low-Pass Gates (LPGs) - a 'vactrol' being an optoelectronic component employed by Don Buchla, the pioneer of West Coast Synthesis, for those musical purposes for which in East Coast Synthesis a Filter-Amplifier combination would be used.

What a Low-Pass Gate is

A Low-Pass Gate acts as a filter and an amplifier at the same time. When it is opened the sound becomes brighter and louder, when it is closed, it becomes duller and quieter. This simulates a behavior found with all vibrating objects in nature, be it a string, a bell, a plate ... . High-Frequency vibrations consume more energy than low-frequency ones, therefore the former will always decay faster than the latter. As a consequence, sounds shaped by a Low-Pass Gate often appear more natural and acoustic than those shaped by a run-of-the-mill amplifier accompanied by a filter.

What the jacks do

As for this module: Apart from the indispensable audio in-s and out-s for both gates there are two more jacks that serve as openers for each gate. Envelope expects an envelope CV for this purpose, while the Trigger jack expects a clock pulse. The latter will trigger an internally generated ping envelope (the famous 'vactrol ping') and only comes in when Envelope is not patched so no envelope CV is supplied.

What the controls do

• Decay controls the notorious sluggishness of the emulated vactrols and therefore determines the actual ring-out time of the gates. In case the gate is opened by a simple trigger, as described above, a low value of Decay will result in pizzicato-like sounds, a medium value in mallet-like sounds and a high value in sounds that are bell- or gong-like.
• Color determines the extend to which high frequencies will be damped.
• Level controls the loudness of the output.