Doepfer A-101-1 Vactrol Steiner Filter - Manual (Page 5)

doepfer System A - 100 Vactrol Multitype Filter A-101-1
5
Pay attention that the notch filter does not arise from a
combination of low pass and high pass only - as one
would expect. Even the band pass control has to be
turned up. The reason for this behaviour are the phase
conditions inside the filter circuit.
Band pass with offset means that a share of all frequen-
cies passes the circuit. High pass gate means that the
filter frequency setting also affects loudness but not only
the frequency.
Of course the controls can be adjusted to any values to
experiment with different mixtures. The table shows only
some typical examples.
If different audio signals are fed into the filter inputs the
output is the sum of the input signals with each input
filtered to the corresponding filter type, frequency and
resonance settings. Consequently a frequency and reo-
nance depending mix appears at the output.
Basics about the different filter types (low pass, band
pass, high pass, notch) and the resonance function can
be found e.g. in the manual of the A-121 Multimode
Filter.
) a Out 1 / )b Out 2 (sockets)
These are the two audio outputs of the module. Output 1
is the output of the original circuit. In the original circuit
the output level distinctly depends upon the resonance
(higher resonance = higher output level). Output 2 com-
pensates this behaviour by the usage of an additional
vactrol that is connected in series to the vactrol that
controls the resonance. This additional vactrol forms a
simple VCA that compensates the level increase for
higher resonance settings to a great extent (but not
perfect).