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AM2000 Module - Eµ VCA
Overview This module is a clone of the single VCA in the Eµ Modular, the 2000. Whilst the performance of this VCA has been well and truely superceeded by modern designs, its still
nice to have an original Rossum designed VCA. The Eµ VCA does have linear and exponential control modes, and it is very similar in design to the Roland 704 VCA from the System 700 Modular.
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 2000 VCA module is based around a CA3080 chip with a pair of NPN/PNP transistors for the exponential converter (called the MP-1 by Eµ -
Matched Pair 1). The linear and exponential control voltages and signal paths use 556 Op Amps, which are higher quality than the contemporary LM301 and 741's, but no longer manufactured.
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. The SSM2010 chip is very hard to locate (make that impossible...), so a clone has not been attempted of the Revision 2 design.
AM Circuit
The clone is exactly the same as the original with a CA3080 core but with NE5532 Op Amps. The exponential converter has been built from a matched pair of 2N3094/2N3906's put on an 8 pin DIL header. I have added a LED driver circuit to drive an ocean blue LED for normal signal levels.
Panel The front panel is a standard AM design, 90mm wide and 4U high, with black lettering. Controls knobs are standard Eµ Modular designs.
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 Resources
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 * AM FAQ's more »
* Hard to find Parts more »
* Eµ Modular Catalog more »
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* AM2000 Project Notes
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* AM2000 PCB layout
Zipped .BRD Eagle CAD
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* AM2000 front panel
Zipped .FPD Front Panel
Designer file |
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Front Panel - mock up |
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PCB - populated |
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