Doepfer A-100(~ 40 MB) - Manual (Page 81)

doepfer System A - 100 A-102 • A-103
1
1. Introduction
Modules A-102 and A-103 are voltage controlled
low-pass filters that filter out the higher parts of the
sound spectrum and let lower frequencies pass
through. Both filters very similar to the A-120 low-pass
filter but sound very different. In contrast to the 24dB
low-pass A-120 - that is based on the famous Moog
transistor ladder - A-102 and A-103 use different
ladder types. The A-103 is an 18dB low-pass that
works with a modified transistor ladder identical to
the circuit used in the Roland TB-303 (base and collec-
tor of each transistor are connected). In the A-102 the
transistors in the ladder are replaced by diodes cau-
sing the typical diode filter sound with a very specific
frequency and resonance behaviour.
The cut-off frequency determines the point at which
filtering takes effect. You can control this manually, or
by voltage control for both filters (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.
CV 1
Resonance
CV 3
CV 2
Audio In
Level
Audio
Out
CV 2
Frequency
A-102
A-103
CV 3