Doepfer A-100(~ 40 MB) - Manual (Page 105)

doepfer System A - 100 Multitype Morphing Filter A-107
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1. Introduction
Module A-107 is a completely new voltage controlled
filter that has available 36 filter types: different versi-
ons of low pass, high pass, band pass, notch, all pass
and filters with new response curves that have no
name up to now.
Of course the standard VCF controls are available:
manual and voltage control of filter frequency and
resonance. For the filters of the first group (1...18)
self-oscillation is possible, the filters of the second
group (19...36) do not feature self-oscillation. On top of
it a final VCA is available - even with manual and
voltage control. All external control inputs are available
twice: one with attenuator and one without.
The 36 filters are organized in two groups of 18
filters each. The filters can be arranged in 64 different
filter chains. Each chain consists of 32 steps. The
sequence of a filter chain is passed through while the
manual control is operated or the external control
voltage changes from 0...+5V. 64 filter chains can be
programmed by the user and stored in the non-volatile
memory of the module.
The transition between filters can be soft (morphing)
or hard (switching). The morphing time (manual and
voltage controlled) defines the transition time between
succeeding filters from a few milliseconds (switching)
up to about 10 seconds.
Additionally a "clocked" mode is available. This
means that the steps of the currently selected filter
chain are selected one after another. Each positive
transition of the Clock signal calls up the next filter of
the chain. A positive trigger at the Step Reset input
resets to the filter of the chain that corresponds to the
momentary step CV. This allows e.g. to switch bet-
ween the filters of the currently selected filter chain in
sync with a sequencer.
The filter design is 100% analog (CEM filter chip).
Only the morphing control and memory managing is
carried out by a microcontroller.
Remark: Because of technical reasons the transition
between the two filter groups cannot be carried out soft
as capacitors have to be switched. Soft transition (i.e.
morphing) is possible only between the filters of each
group (i..e. within the filters 1...18 or
19...36). Switching
between filters causes a "click" if the filters are from
different groups.