doepfer
System A - 100
18dB Low Pass
A-103
1
1. Introduction
Module
A-103 (VCF 6)
is a
voltage controlled low-
pass filter
with a
cut-off slope
of
-18dB/octave
. It
filters out the higher parts of the sound spectrum and
lets lower frequencies pass through.
The
Cut-Off Frequency
determines the point at which
filtering takes effect. You can control this manually, or
by voltage control (
filter modulation
, for instance by
an LFO). Three CV inputs are available, and the sum of
the voltages from these affects the filter cut-off.
Resonance
(or Emphasis) is adjustable all the way up
to self-oscillation - in which case the filter behaves like
a sine wave oscillator.
A-103 uses a so-called
transistor ladder
with a slope
of 18 dB/Octave as frequency controlling element. It is
very similar to the transistor ladder of the A-120 (24dB
Moog type low pass) but the ladder of the A-103 is a
modification of the original Moog ladder and identical to
the ladder used in the
Roland TB-303
(base and
collector of each transistor are connected).
CV 1
Resonance
CV 3
CV 2
Audio In
Level
Audio
Out
CV 2
Frequency
A-103
VCF 6
CV 3
