EMS Synthi - The Envelope Generator

In the EMS world what we normally refer to as the Envelope Generator is called a "Envelope Shaper". There is a good reason for this as it's definitely not your usual ADSR. 

The envelope can take the shape of a trapeziod, so is often referred to as a "Trapezoidal Envelope Generator."

It's actually a Envelope Generator + a VCA rolled into one.
The Shaper operates by generating a CV & using it to control a VCA.

The Synthi's Shaper has 6 knobs (4 red & 2 silver) & 2 outputs (Trapezoid Out & Signal Out).

The last two silver knobs (5 & 6) are called Trapezoid & Signal.
These set the level (amplitude) of the two outputs.(more about this later).

The first four red knobs are the Envelope Gen itself.
They are named: Attack, On, Decay, Off.

1. Attack is what you'd expect.(2ms to 1sec)
2. On = the time the envelope stays at the top level reached during the attack phase.(0-2.5secs)
3. Decay - again what you'd expect (3ms - 15secs)
4. Off = This is like having a built-in LFO. The length of time the envelope is off (between the end      of  the last envelope & the start of the next env)

The knob associated with this "off section" (see picture below) is unusual as it has two ranges/stages.
4a. While in the range of 0-6 we have an automatic retrigger ---
    it will lengthen the automatic off time between 0.5ms to 5 secs

4b. After about level 6 the cycle starts go into manual mode.... to trigger
    the envelope we can use the trigger button that sits next to the joystick.

 

Dials 5 & 6 control the

5. Trapezoid Level: This is just the CV level - what you'd expect from a standard Env Gen.
6. Signal level: This uses the Synthi's built in VCA.
   The useful thing about this is you can just patch a oscillator into the Env Gen and obtain a sculptured output without the need to patch a VCA

The two envelope shaper outputs : Trapezoid (row 11) & Env. Signal (row 12)

Voltage control options for the envelope shaper is limited to the decay. 

To do this place a pin in row L.

 

The synthi E also has a trapezoidal EG. 

The shapes are displayed  on the synth itself.

 

Links:

1. Analogue Solutions.

2. Video (Youtube)

3. Muffs

4. Sound On Sound

5. EMS Synthi-E - Trapezoidal Envelope Generator