Doepfer A-101-9 Universal Vactrol Module - Manual (Page 5)

DOEPFER DOEPFER DOEPFER DOEPFER System A-100 Universal Vactrol Module A-101-9
5
4. Controls and In- / Outputs
2 Man.: manual vactrol resistance control
! CV In: control voltage input
1 CV: polarizer for CV input
This group of elements is responsible for the current vactrol
resistance. Knob 1 Man is used to adjust the vactrol
resistance manually. Turning this knob clockwise reduces
the vactrol resistance and lights up the display LED
3 . A
CV input ! is available to control the the vactrol resistance
by an external control voltage (e.g. LFO, envelope follower,
random, ADSR, keyboard CV, sequencer, theremin, ribbon
controller, foot controller, Midi-to-CV, ...). The CV input is
equipped with a polarizer. In principle a polarizer is an
attenuator, but in contrast to a normal attenuator it enables
both positive and negative attenuations (i.e. amplifications in
the range -1...0...1). Negative attenuation means that the
signal is inverted (please refer to the manuals of A-133 CV
Polarizer or A-138c Polarizing Mixer for details). The middle
position of the polarizer control corresponds to full
attenuation (or amplification = 0). This is the same as the
fully counterclockwise position of a "normal" attenuator. The
fully clockwise position of the polarizer corresponds to
amplification +1 (i.e. the signal passes unchanged), the fully
counterclockwise position corresponds to amplification -1
(i.e. the signal is inverted).
" a VAC1: vactrol 1 connector
" b VAC2: vactrol 2 connector
3 VAC control: LED display
The sockets " a and " b make available the terminals of the
two vactrols of each sub-unit. In contrast to most other A-
100 sockets these sockets are not grounded, i.e. the two
terminals of the vactrol are connected to the two terminals of
the socket in question. The resistance of the two vactrols of
each sub-unit changes simultaneously. The reason is that
for some applications two simultaneously changing resistors
are required (e.g. for some filter circuits).
The LED
3 displays the current vactrol resistance. A dark
LED indicates a high resistance, a bright LED a small
resistance. The minimum resistance range for each vactrol
is about 1 k
Ω (fully bright LED) to 500 kΩ (completely dark
LED) but the actual resistance range varies a bit due to the
vactrol tolerances (minimum value 500
Ω ... 1 kΩ at fully
bright LED, maximum value 500 k Ω ... 2 MΩ at completely
dark LED). For more general details about vactrols please
look at the Vactrol basics page on our website
www.doepfer.com.