Dual Decay/LFO

Module A-142-5 contains two simple envelope generators which can work also as A/D LFOs. For the switching between envelope and LFO the toggle switch "Loop" is used. When in position "off" the unit in question works as an envelope generator and the envelope is triggered by the positive edge of the trigger signal applied to socket "Trig.". The trigger inputs are normalled (1->2).
When the Loop switch is in position "on" the unit in question works as an LFO.
The module features a control input "VCL" (voltage control loop). A high level applied to this socket turns loop "on" and the unit works as an LFO provided that the switch is in "off" position. The VCL input expects a digital high/low signal and the voltage level has to be about +3.5V or more to activate the switching.
When a trigger signal is applied in LFO mode the envelope and LFO interfere with each other.
Each unit has a Decay control that is used to adjust the decay time manually in the range 2 ms ... 2 seconds (?). The attack time can be adjusted internally by means of a separate trimming potentiometer for each sub-unit in the range 1 ms ... 15 ms. The factory setting is about 3 ms. This is the attack time of the TB303.
The signal appears the envelope/LFO output "Out". The peak voltage is about +10V. The signal is displayed by an LED.

Suggestions for modifications:

By changing the value of a capacitor the time range can be modified (e.g. 0.2 ms ... 0.2 seconds or 20 ms ... 20 seconds)

Release date: summer 2026 (without obligation)

https://doepfer.de/a1425.htm