Doepfer A-106-1 Xtreme Lowpass/Highpass Filter User Manual
Doepfer Audio

DOEPFER
DOEPFER
DOEPFER
DOEPFER
System A-100
X-treme Filter A-106-1
1
Fig. 1: A-106-1 Controls and In/Outputs
1. Introduction
Module A-106-1 is an unique low/high pass filter and has it's
origin in our experiments to built a MS20 filter clone. In
contrast to other filter designs it has different audio inputs
for low and high pass, but only one audio output. The type
of filter (12dB low pass, 6dB high pass or any mix) is
defined by the shares of the audio signal fed to the
corresponding inputs. Even two different audio signals can
be used as low and high pass input. A special feature is the
polarizer at the high pass input that allows to add/subtract
the high pass to/from the low pass share, leading to pseudo
band pass and notch responses (details concerning pseudo
in the next chapter).
Another special feature are the clipping controls, which
allow independent adjustment of the positive and negative
clipping level. The resonance goes up to self-oscillation, but
with a clearly different behaviour than on other filters. At
certain resonance and clipping settings the self-oscillation
generates rectangle or short sawtooth shaped pulses.
In general the A-106-1 is a very strange and awesome filter
and far away from being perfect (e.g non-linear control
scale, self-oscillation with all sorts of waveforms except
sine, a lot of roaring, rattling, noise or other unpredictable
sounds at high distortion and resonance settings, high
distortion or audio level overrides the resonance, significant
CV feedthrough …). But the A-106-1 has a lot of character –
probably much more than any other filter of the A-100 – and
is able to generate filter sweeps which are not possible with
any other filter.