Doepfer A-123 24dB High Pass (no longer available) - Manual (Page 5)

doepfer System A - 100 VCF 4 A-123
5
$ QCV
This socket is the voltage control input for the filter’s
resonance.
If you patch a modulation source (eg LFO, ADSR) to
this input, the resonance of the filter will be modulated
by it: increases in voltage will increase the amplitude
of the frequencies around the filter cut-off point.
% Audio Out
Filter output % sends out the filtered audio signal.
5. User examples
The filter’s cut-off frequency can be modulated in
various ways:
• VCF - LFO
Modulation of the cut-off frequency produces cycli-
cal changes of the sound spectrum. At low
frequencies (c. 1 - 5 Hz), you get a "Wah-Wah"-
effect. Modulation in the audio range produces
interesting sounds; the same principles apply here
as with frequency modulation of the A-110 VCO
(see chapter 6).
• VCF - ADSR
Modulation by an envelope results in gradual
change of the sound spectrum. Typical uses
include filter sweeps, which slowly sweep through
the audio spectrum, picking out different harmonics
in turn.
• VCF - Keyboard CV
This modulation produces pitch-related filter ope-
ning.