User Manual

doepfer

System A - 100

VCF 4 A-123

$ 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.