Search dance music

Notes: Another update for WMD's clever dual VCA, this time a little bigger to give more control. Digital control of CV and attenuation gives lots of creative options. Third time's a charm.

Supplier's Notes:
WMD have done several designs of this circuit over the years, the first one had no knobs, the second was too small, the MKIII is finally how this circuit should be packaged. This module does some really cool stuff and is super useful in any system.

The Digital VCA lets signal through like a normal VCA, but the CV and attenuation level is controlled digitally. This lets us do things like wait until there is a zero crossing to change the amplitude, resulting in clickless amplitude changes.

The Trigger mode causes the VCA to only update when a trigger is received. The addition of a noise circuit for each side let us do a very quick and easy sample and hold that never droops. With no input, 5V is normaled to the attenuator, so you get a 0-5V sample and hold. In Bipolar mode, you can get -5 to +5V.

Both sides have bipolar VCA mode (polarizer), which lets them invert the signal when negative CV comes in. Also known as ring modulation. With the zero crossing detector, this can produce some super wild wave shapes.

Features

Dual VCA Design
Unipolar or Bipolar Operation
DC Coupled Analogue Signal Path
Low Distortion / Low Noise
VCA Closes Completely
Zero Crossing Detector Mode
Trigger Mode
Two Independent Noise Sources
8 bit CV resolution
Great for Fast Envelopes and Sine Bass Sounds

Specifications

Power: +65mA, -45mA
Width: 8HP
Depth: 35mm with cables
Height: Eurorack 3U (128.5mm)
Board Height Behind Panel: 112mm
CV/Signal Input Impedance: 100k
Output Impedance: 1k
UPD in 3.3V Threshold Schmitt Trigger
ZCD produces 15us 5V pulse
5V CV to fully open VCA
Linear VCA response
20Vpp signal handling