Access Virus Rack XL, User Manual

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CHAPTER 5
Introduction
In the sound program we are using for our ex-
periments, both filters are selected, so that all
adjustments to the given parameters affect
both filters. However, you have yet to actually
hear the effect of Filter-2 on the signal because
it is mixed out of the audible signal path of the
Virus.
Before we get started with our next experiment,
deactivate SATURATION, set the ENV AMOUNT
of the filter envelope to zero and set CUTOFF 2
to the center position so that Filter-2 always has
the same cutoff frequency as Filter-1 (we’ll ex-
plain CUTOFF 2 a bit later). Set CUTOFF to a
medium or middle value and turn the RESO-
NANCE encoder counter-clockwise to the far
left to achieve a relatively muddy sound.
Now locate the FILTER BALANCE parameter in
the FILT menu and rotate it from the left to the
right. You will note the sound becomes muddier
as you turn the encoder towards the center po-
sition and that the sound is somewhat brighter
at the far right of the control range then at the
far left.
The reason for this effect is that when you turn
the FILTER BALANCE to the far left, only Filter-
1 is audible. When you rotate the parameter to
the right, Filter-2 is blended in so that it follows
Filter-1 in the signal chain. When you turn the
FILTER BALANCE clockwise, Filter-1 is blended
out of the signal chain until at the far right posi-
tion only Filter-2 is active and audible.
Each filter in the Virus normally features 2 poles.
However in the FILTER ROUTING operating
mode SER 6, Filter-1 operates with 4 poles, so
the signal patched through Filter-1 (FILTER
BALANCE to the far left) is trimmed more dras-
tically than when it is routed through Filter-2
(FILTER BALANCE to the far right). When you
set the FILTER BALANCE to the center position
(12 o’clock) - as we mentioned before - the two
filters are routed in series, which means they re-
spond as if they were a single filter with 6 poles
and consequently a great deal of slope. This is
why the input signal is trimmed substantially
when you set the parameter to this position.
Experiment with the diverse FILTER BALANCE
values to get a feel for the different degrees of
slope. Rotate the CUTOFF encoder or activate
the filter envelope (for both filters!) to hear the
filters in action.
The CUTOFF 2 parameter is a special feature: It
controls the cutoff frequency of the second fil-
ter, but is subordinate to the CUTOFF encoder
located above it. In other words, at the center
position (12 o’clock) the manually selected fre-
quency of Filter-2 is identical to that of Filter-1.
When you rotate the encoder to the left the cut-
off frequency level of Filter-2 is increased rela-
tively to Filter-1, when you turn to encoder to
the right the cutoff frequency level is decreased
relatively. Now when you adjust the CUTOFF,
you adjust the cutoff frequency of both filters by
the same measure! This feature lets you deter-
mine a difference in values in the filter frequen-
cies (called an offset) via the CUTOFF2 encoder
which remains constant whenever you adjust
the CUTOFF encoder.
Yet another experiment in which you can come
up with new filtering characteristics that are
typical of the Virus:
Set FILTER BALANCE to the center position
(12 o’clock) and CUTOFF 2 to the maximum
level. The FILTER ROUTING operating mode
must remain SER 6. Set CUTOFF and RESO-
NANCE to a middle value and select a clearly
audible SATURATION curve.
Now you can filter this complex signal pro-
duced by a combination of the saturation stage
and the Filter-1 yet again. Rotate the CUTOFF 2
encoder slowly towards the center position (12
o’clock). You can hear how Filter-2 gradually
modifies the distorted signal. You can set a
RESONANCE value for Filter-2 if you choose