Erica Synths DIY Polivoks(ish) ADSR EG kit - Manual (Page 5)

HOW IT WORKS?
GENERALLY, ERICA SYNTHS ENVELOPE GENERATOR CONSISTS OF:
* Input/knob control voltage section
* Control voltage multiplexer
* Slew rate controlled integrator charge/discharge circuit that tracks target level and sensing
* Control logic with gate and trig inputs
* Output
Logic selects with level to track at with rate. This select (2 or 3 bit) is passed to multiplexer that
selects two control voltages out of many available. One for tracking rate, the other one - target
level. Normaly EG rests in idle state, that tracks idle voltage (normaly 0V) with release rate. As
soon as EG is triggered, logic selects next stage for the tracking circuit and it enters the attack
stage. During this stage, analog multiplexer sets attack rate and attack voltate to tracking
circuit, and voltage on the output rises until it reaches the set level. As soon as the set level is
reached, logic advances to the next stage, that is decay/sustain stage. In this stage, tracker
circuit tracks sustain control voltage with the dacay rate for as long as key (gate) is not
released. At any time, as soon as key gets released, logic sets release/idle state. In loop mode,
logic enters attack stage as soon as release stage is completed.
Trigger and gate inputs are filtered against spike glitches. Tigger input can be fed with gate
signal or any signal of any duration, as it also has duration limiting circuit. Gate and trigger
inputs can be set to any polarity using jumpers. Selecting active high means that pressing and
holding a key on the controlling keyboard produces a more positive pulse relative to idle voltage
on the trigger input, and gte stays on higher voltage until the key is released. Active high
controls are Roland and Sequential Circuits compatible, while active low setting is for Korg and
Moog compatibility. Gate and trigger input levels can be set independantly for compatibility
with absolutely any sources. Both inputs have an option for pull-up resistor in case a compati-
bility with korg modular analog is needed.
Tracking circuit tracks any set voltage target points from -10V to +10V, with rate control voltage
from approx -0.65 to +10V. The higher the rate control voltage, the faster it tracks the target
voltage. As analog multiplexer is not fit to switch bipolar 20Vp-p signals, control voltages are
scaled before and aſter the ic.