Doepfer A-100(~ 40 MB) - Manual (Page 313)

doepfer System A - 100 Fixed Filter Bank A-128
5
Creating a multi-band equalizer
The patch in Fig. 4 shows how to model a simple
graphic equalizer. An A-138 Mixer is used to mix the
following signals:
• Input 1: the signal from the audio output of the fil-
ter bank, via an A-175 inverter.
• Input 2: the signal from the audio output of the fil-
ter bank.
• Input 3: the original signal
Using the mixer pots "In 1", “In 2” and "In 3", you can
control the relative mix of the signals :-
• In 1: Amount of cut
• In 2: Amount of boost
• In 3: Amount of original signal
To model an equalizer, you adjust the mixer pots as
per the above table. Naturally, any mix is possible, by
adjusting the pots according to the following formula :
Audio Out = - In 1 • filter signal
+ In 2 • filter signal
+ In 3 • original signal
P Patching a VCA in before the mixer’s inputs
can give voltage control of the relative
amounts.
Fig. 4: Creating a multi-band equalizer
A-128 A-175
Audio
In
Input 1
Output
A-138
MIXER
Input 2
Input 3
In 1
In 2
In 3
Out
Audio
Out
Pot
just the
original just the
filter bank
original
+ boost original
+ cut
In 1 0 0 0 0 ... 10
In 2 0 10 0 ... 10 0
In 3 10 0 10 10