Doepfer A-101-9 Universal Vactrol Module - Manual

DOEPFER DOEPFER DOEPFER DOEPFER System A-100 Universal Vactrol Module A-101-9
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Fig. 1: A-101-9 Controls and In/Outputs
1. Introduction
We call the A-101-9 an Universal Vactrol Module. It contains
two identical sub-units. Each unit has two vactrol outputs
available that are controlled manually and by an external
control voltage with polarizer. A vactrol is a combination of a
light depending resistor (LDR) and a light emitting diode
(LED) both put into a small light-proof case. For more
general details about vactrols please look at the Vactrol
basics page on our website www.doepfer.com. Increasing
the LED brightness causes a decrease of the LDR
resistance. The LED at the front panel displays the
brightness of the LEDs of the vactrol pair in question. The
resistances of the two vactrols of each sub-unit change
simultaneously. This allows to control two parameters at the
same time or to control a parameter that requires two
variable resistors (e.g. frequency for certain filter circuits).
The LDR terminals of each vactrol are connected to the jack
sockets labelled VAC1 and VAC2.
Applications: A-101-9 introduces voltage control to any
function that is controlled by a fixed or variable resistor (e.g.
a two-terminal normal or trimming potentiometer). There are
many applications within the A-100 (e.g. Attack, Decay,
Release of envelope generators, time of slew limiters and
trigger delays, random rate of noise module). But the
module can be used even outside the A-100 in combination
with any other circuit that uses a variable or fixed resistor to
control a parameter (e.g. wah-wah or parameters of guitar
stomp boxes). Even for "circuit bending" the vactrol outputs
can be used.