Operation Manual

6.101 Vlowpass2 160
equal to a 0.08333 value.
• MIDI channel: MIDI channel used by the keyboard.
6.101 Vlowpass2
The Vlowpass2 module is a voltage-controlled second-order low-pass fil-
ter (-12dB/octave). This module has three inputs and one output. The first
input is the signal to be filtered, while the second and third inputs are mod-
ulation signals which are used to vary the cutoff frequency of the filter. The
amplitude of the two modulation signals is adjusted with the two gain knobs
mod1 and mod2 respectively. The output is the filtered signal.
Tuning the Cutoff Frequency
The cutoff frq knob tunes the cutoff frequency to the desired level. The vari-
ations in the cutoff frequency, caused by changes in the modulation inputs,
are relative to this level. The resonance knob is used to emphasize the frequencies near the cutoff
frequency as shown in the following figure:
res=1
res=0.5
res=0.1
res=0.02
cutoff
frequency
frequency
Hz
-12dB/Oct
amp
dB
Figure 102: Frequency Response of Vlowpass2.
Cutoff Frequency Variation
The amount of variation of the cutoff frequency obtained with the modulation inputs depends on
the adjustment of the mod1 and mod2 gain knobs. The total modulation signal is the sum of the two
inputs each multiplied by the gain corresponding to its respective mod knob. When the mod knobs
are in the center position (green LEDs on), the gain equals 1 and the pitch variation is 1 Volt/octave.
When the modulation signal is the pitch output from a Keyboard module, this position can be used
to make the cutoff frequency follow an equal temperament scale. The modulation signal of the
second input can be inverted by pressing the inv button. This can be useful when generating bass