Doepfer A-103 18dB Low Pass - Manual

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