SSSR Labs SM630 AWS

Description

Analog non-linear waveshaper with voltage controlled gain and symmetry, and selectable working mode: 3 different colors of shaping.

SSSR Labs AWS is the first collaborative design by Dmitry Shtatnov and Vyacheslav Grigoriev. The module is inspired by the «Harmonics» waveshaper section of the Soviet monophonic keyboard synthesizer, Alisa-1377. Hense the name: Alisa Wave Shaper. The circuitry partially resembles the original schematic, but goes beyond that, adding a full voltage control to it.

The principle of operation is based on folding VCA with VC balance of the differential stage, followed by two non-linear processing stages, emphasizing the small non-linear window near the zero-crossing region. The Color switch adds a special feedback loop inside this circuitry, and a filtering stage, ending up in three differently sounding working modes.

This module is dedicated for harmonically poor waveforms, such as sinewave or triangle, but interesting effects can be reached using the AWS with sawtooth or other waves with smooth transient stages, such as a filtered analog oscillator, or a wavetable oscillator, such as SM042 Kotelnikov. The square wave is not processed by this module.
AWS also can process LFO, EG or a simple DC offset. The non-linear function is persistent for each unit, and uniform over the full frequency range including DC, so it can transform a simple envelope waveform or a sequence into something very complex and unpredictable.

Drive Knob controls the gain of the VCA, and CV Input for this function is attenuated by the DRIVE CV knob.
The same is with symmetry (SYMM).
Quickly changing symmetry can be described as a pulse width modulation applied to any waveform.