DOEPFER A-100 Series User Manual

A-123
VCF 4
System A - 100
doepfer
6
24 dB notch filter with voltage control of
middle frequency and bandwidth
The patch in Fig. 3 shows a 24 dB notch filter with
voltage-controlled middle frequency and bandwidth.
Fig. 3: 24 dB notch filter with voltage control of
middle frequency and bandwidth.
For this patch, set both f
L
(L ow Pass A-122) and f
H
(H igh Pass A-123) to roughly equal cut-off points
(judging by ear).
Use a control voltage "FCV" to alter the middle fre-
quency f
M
of the notch filter: f
M
= (f
L
+ f
H
) / 2.
Use a control voltage "BCV" to alter the bandwidth,
which is determined by how far apart the two filters’
cut-off frequencies are. Using the A-175 Voltage
Inverter, these frequencies
f
L
and
f
H
are altered sym-
metrically around the middle frequency (see Fig. 4).
Fig. 4: Effect of FCV and BCV on the notch filter’s
response.
f
H
Freq.
Ö
A-122
Freq.
Ö
A-123
Freq.
Ö
f
L
A-138
Freq.
Ö
f
M
A-175
Audio
In
FCV
BCV
Audio
Out
CV 1 CV 2
CV 1 CV 2
Freq.
Ö
FCV
BCV
f
M

DOEPFER A-100 Series Specifications

General

Type	Modular Synthesizer System
Manufacturer	Doepfer Musikelektronik GmbH
Power Supply	External Power Supply
Current Consumption	Depends on modules installed
Dimensions	Varies by case size
Number of Slots	Varies by case size
Width	Varies by case size