Serge 1973 Envelope Generator and Triple Switch

serge-eg-switch-panelThis 5U panel contains three CGS Serge PC boards.

Serge Envelope Generator

It’s an early Serge design that is not a conventional envelope generator.  It is in fact a linear Attack-Release EG, voltage controlled, that operates somewhat like the other Serge slewing modules, the Positive and Negative Slew, and Universal Slope Generator.  There is not a lot of functional description on Ken Stone’s page, so I will provide a little.

A trigger or gate into the Start input will begin an AR cycle.  The output will rise to full voltage (around 6 volts) at the rate set by the Rise pot, and then fall back to zero at the rate set by the Fall pot.  Both rise and fall times can be voltage-controlled via the CV input, which has a reversible attenuator (Blue knob).

The End output is high when the output is at zero and falls during an active cycle.  Patching End to Cycle turns the module into an LFO or VCO with a variable rise and falling ramp wave.  It will go quite high into audio frequencies, but does not go extremely slow as an LFO.

A gate patched into the Cycle input will cause the module to go into cycling mode at the rise and fall rates, making it a kind of gated LFO or VCO.

Now there is more!  The Window output is a pulse that goes high and low at some point during the cycle.  The threshold for the window transition is set by a pot, together with a CV input.  This pulse can be used for complex pattern generation.

Finally, the Hold input will cause the output to hold its value at the time a positive gate is sent to it, but only when the Window output is high!

Triple Bi-Directional Switch

This is a group of three independent electronic switches that can route two signals to one output, or one input to two destinations.  When the Control input is not patched or low, the X jack acts like a wire to the Y2 jack (actually it has about 2K resistance).  Signals of up to about +/- 7 volts can be conveyed without distortion.  I changed the suggested labeling from ‘B’ to ‘X’ and from ‘A1’ and ‘A2’ to ‘Y1’ and ‘Y2’.

Construction Photos

Note that no passageway was needed to route wires through the bracket, because each side contains one envelope generator.  All power is pigtailed from a single power header.

serge-eg-switch-back-1The other side.



One Response to Serge 1973 Envelope Generator and Triple Switch

  1. Fer says:

    Thank you so much for this excellent 73 Env Gen functions description!

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