Softube Doepfer A-101-2 Vactrol LPG

• 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.​

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.

Gongs, Plucks, Twangs, and More
Organic, buttery, warm, woody, rubbery, musical, natural, acoustic — these are words that commonly describe the character a low pass gate module can add to synth patches.

Expertly Made Presets
Buying this module gives you over thirty new and inspiring presets, instantly putting the Doepfer LPG to excellent use in your Modular rack.

A classic concept extended
Originally, the low pass gate was invented by legendary synth pioneer Don Buchla. Doepfer has expanded on the golden concept of the master by adding clever features, not least the Resonance control which can add anything from a subtle nuance to screaming resonance, and further into self-oscillation.

This expands the capabilities of the module, changing it from a mere controlling tool into an additive, creative one. Start by sculpting a simple waveform into a xylophone, then burn it up into a wailing, fire-breathing dragon... all with one module.

Vactrol control
The hardware Doepfer LPG modules are based on vactrols, just like opto compressors. The response time of these can vary wildly, which is part of the LPG charm. Softube's plug-in version of the Doepfer LPG adds the Vact switch which is not part of the original hardware. This lets the user select between a fast, medium or slow response time, to cover the variation between individual analog units.

Being able to offer something in software that doesn't exist in hardware is a thrill for us here at Softube, but we never do it if it means compromising on quality. Luckily, we were able to get our hands on, and model the characteristics of, multiple modules to bring this feature to life.

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