Manual
The top level filter parameters we just described effect all active filter poles the same. They
override the individual pole settings.
The High- and Low-buttons and the four individual pole knobs affect each pole individually.
The High/Low-buttons:
By pressing the
(High/Low)
-button, each pole can be set to Lowpass or Highpass. The
corresponding
<LED>
shows the active filter type for each pole. Highpass allows higher
frequencies to pass and cuts off low frequencies, whereas Lowpass does the opposite.
The Pole-knobs:
Use the
(Pole)
-knobs to set the cutoff frequency of each individual pole. This means you can
set the frequency where each individual pole begins to filter. The settings of these knobs
define the filter slope of the entire filter. The closer the knob settings resemble eachother,
the steeper the filter curve of the entire filter will be.
Using both the High/Low buttons and the Pole knobs, you can set the characteristics of the
filter in a very flexible way.
Let’s take a look at a fully elaborated example. This example will guide you through the
entire filter section in a more practical way. To keep it as simple as possible, we won’t tweak the
resonance and envelope settings yet.
Load Single-Sound Nr. 255 ‘Initial Patch’.
Lowpass
1. Both
< LED’s 2/4-Pole >
light. All four poles are active.
2. All four
< LED’s High/Low >
indicate <Low>. This means all four poles are set to Lowpass.
They filter out the high frequencies.
3. Turn all four
(Pole)
-knobs fully anticlockwise. Each individual pole now has the same cutoff
frequency. The entire filter now has the steepest possible curve, which means 24dB. You’ve
just built a classic 24dB Lowpass filter! You can now use the
(Cutoff)
-knob to define the
frequency where the filter starts working. When turning it fully anticlockwise, you won’t hear
anything at all, since the cutoff frequency will be below the audible range. Everything above
that frequency is filtered out of the signal.
4. Now turn all 4
(Pole)
-knobs fully clockwise and then turn the
(Cutoff)
-knob over its entire
range. You still have a 24dB Lowpass filter (all pole knobs have the exact same setting, which
means the steepest filter slope). The Cutoff knob now has a different range.
5. Turn all
(Pole)
-knobs to the middle. The filter still has a 24dB/octave slope. The range of the
cutoff knob has once again changed.
Filter slope
Now we want to change the filter slope and thereby its characteristics. As you probably
suspect, the individual pole knobs must have a different position for each one of them.
Turn
(Pole)
-knob
1+2 fully anticlockwise
and
(Pole)
-knob
3+4 fully clockwise.
You’ve now
halved the filter slope to 12 dB. You have now built a 12dB 2 pole filter! Its sound contains
more high frequencies, it sounds more silkier and it also seems smoother. It reminds us a bit of
the old SEM filter. You (almost) get the same result when doing the opposite by turning pole
1+2 fully clockwise and pole 3+4 fully anticlockwise.
VCF Filter
3-6
037
Single Mode
thebook-all 07.11.2002 18:28 Uhr Seite 37 (Schwarz Bogen)
