Owner's manual

doepfer
System A - 100
Vactrol Lowpass Gate
A-101-2
1
1. Introduction
Module A-101-2 is a vactrol based combination of
Low Pass filter (LP) and VCA. Additionally a combined
mode LP+VCA is available. In this mode the sound
becomes more dull as the loudness decreases.
The A-101-2 was inspired by module 292 of Don Buchla.
He also intruduced the term "Low Pass Gate" for this
combination of functions.
The function of the module is controlled by a manual
switch or by two gate inputs.
In principle the A-101-2 is a 12 dB low pass that can be
switched to VCA or a combination of Low Pass and
VCA. The controlling elements for frequency resp. loud-
ness are so-called vactrols. A vactrol is a combination
of a light depending resistor (LDR) and a light emit-
ting diode (LED) both put into a small light-proof case.
Vactrol based circuits are known for their soft low-
distortion sound. For details about vactrols please use
the corresponding link in the A-101-2 info page on our
web site www.doepfer.com.
Frequency resp. loudness is controlled manually and
by two control inputs.
The audio input is very sensitive in filter mode to obtain
distortion effects if desired.
The resonance function "colors" to the sound and is
adjustable all the way up to self-oscillation.
In contrast to the Buchla design the A-101-2 offers the
resonance feature, attenuators for both CV and audio
input, and two gate inputs to control the function of the
module in addition to the manual toggle switch.