AM2005 Module - Eµ Systems VCA

Overview This module is a clone of the single VCA in the Eµ Systems Analog Modular Synthesizer with both linear and exponential control modes.

Original Circuit The original Revision 1 design dates back to the Autumn of 1972 when Dave and Scott were setting up their new synthesizer company in Santa Clara. The VCA control has both linear and exponential control.

From October 1974 the front panel toggle switch had a centre position for simultaneous linear and exponential control. The CA3080 based VCA was a bit noisy, so by 1980 it was replaced by a SSM2010 based version, which improved the S/N ratio and reduced the audio distortion. It is this version that has been replicated, once I had found some extremely rare SSM2010 chips!

Cloned Circuit The clone is exactly the same as the original with a SSM2010 core and TL072 Op Amps. There is a LED for monitoring the audio output signal level.

The module has the following front panel controls:

• Signal Input Level -
• Signal Input Level +
• Initial Gain
• Gain Control 1 and 2
• Mode Switch - Expoenential or linear
• LED - audio output level

There are six 3.5mm jack sockets mounted at the base of the panel, these are:

• Signal Inputs (x3)
• CV Inputs (x2)
• Signal Output

Front Panel The front panel is a standard AM design, 90mm wide and 4U high, with black lettering. Controls knobs are standard Eµ Modular designs.

AM2005