A-143-1

Complex Envelope Generator / Quad AD-Generator / Quad LFO

Overview: Module A-143-1 is a complex envelope generator that consists of 4 Attack/Decay generators. For complex envelope generation the four units can be daisy-chained, i.e. the preceding unit triggers the following unit. The four units can even be used as four separate AD generators (switch position AD) or AD-type LFOs (switch position LFO).

Details: Module A-143-1 contains four separate attack/decay type envelope generators. Each unit can be switched into a free running mode (LFO mode). The LFO mode differs in several ways from a regular LFO (like A-145, A-146 or A-147): The slopes are exponential - in contrast to the linear slopes of a normal LFO, and the frequency is defined by both controls. The attack control defines the time of the rising slope, the decay control the falling slope.

Each unit has a comparator that compares the AD output voltage with a manually adjustable threshold and switches the corresponding comparator output (Cp 1...4) to "high" as soon as the AD output voltage goes in the decay phase and drops below this value. The comparator output is normalled to the trigger input of the next stage via the switching contact of the trigger input socket. Consequently the first unit triggers the second, the second triggers the third and so on.

Each AD generator is equipped with a Polarizer (look at the Voltage Controlled Polarizer A-133 concerning details about the polarizer function) and a mixer that adds up all polarizer outputs. This allows all AD/LFO output signals to be added to the mix output with adjustable level (and optionally inversion). Asingle output (Env 1...4) is also available for each unit.

If the trigger input of unit 1 is controlled by a normal gate signal (e.g. from a keyboard resp. MIDI-to-CV/Gate interface) one obtains a very complex envelope signal at the mix output. The signal contains 8 segments controlled by Attack 1, Decay 1, Attack 2, Decay 2, Attack 3, Decay 3, Attack 4 and Decay 4. The transition between the stages (i.e. when the following AD generator is triggered) is controlled by threshold knob. The positive or negative contribution of each unit to the mix signal is adjusted with the Mixing Polarizer control. If the trigger input of unit 1 is controlled by the comparator output of unit 4 one obtains a 8 stage LFO.

The single AD outputs can be used to control VCAs or VCFs that open one after another corresponding to the AD signals (a little bit similar to the Shepard generator A-191).

The default-connection between the four units (CPn = Trig.n+1) can be interrupted by patching cables into the trigger inputs. Consequently the four units can be used as separate AD generators or LFOs. In all cases the mix signal is available (e.g. mix of four AD generators or LFOs with adjustable level and sign).

In the LFO mode the comparator output serves as an LFO rectangle output with adjustable pulse width (= threshold control).

Each unit is equipped with a separate LED display for envelope and comparator output. The shortest attack/decay time is about 5 ms, the longest attack/decay times are about 3 seconds (attack) / 10 seconds (decay). By changing the value of a capacitor the shortest time can be modified.

A detailed description of the module can be found in the user's manual.

http://www.doepfer.de/a1431.htm