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CHAPTER 4

Introduction

The technical design of this second filter is
identical to the first, so we won’t discuss it in
as much detail as we did the first filter. Howev-
er, there are few differences in how you handle
the second filter:

• Only two control features of the VIRUS are al-
located exclusively to Filter-2: Cutoff-2 and FILT
2 MODE.

• The RESONANCE, ENV AMOUNT and KEY
FOLLOW pots can be allocated to either of the
two filters or both simultaneously. Use the two
SELECT-buttons located at the far right of the
FILTERS section to select the desired operating
mode. For instance, if you press the FILT 2 SE-
LECT button, then the values you set via the
RESONANCE, ENV AMOUNT and KEY FOL-
LOW pots apply exclusively to Filter-2. The
corresponding parameters of Filter-1 remain un-
affected. On the other hand, if you press both
SELECT buttons at the same time, the values
that you dial in apply by the same measure to
Filters 1 and 2.

In the sound program we are using for our ex-
periments, the LEDs of both buttons are illumi-
nated, 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 (12 o’clock) so that Filter-2
always has the same cutoff frequency as Filter-

1 (we’ll explain Cutoff 2 a bit later). Set Cutoff to
a medium or middle value and turn the RESO-
NANCE pot counter-clockwise to the far left to
achieve a relatively muddy sound. Now locate
the FILTER BALANCE pot at the upper right
hand of the control panel and rotate it from the
left to the right. You will note the sound be-
comes muddier as you turn the pot towards the
center position (12 o’clock) and that the sound
is somewhat brighter at the far right of the con-
trol range then at the far left.

The reason for this effect is that when you turn
the FILTER BALANCE pot to the far left, only Fil-
ter-1 is audible. When you rotate the pot to the
right, Filter-2 is blended in so that it follows Fil-
ter-1 in the signal chain. When you turn the FIL-
TER BALANCE pot clockwise, Filter-1 is
blended out of the signal chain until at the far
right position only Filter-2 is active and audible.

Each filter in the VIRUS normally features 2
poles. However in the FILTER ROUTING oper-
ating 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 drastically than when it is routed through
Filter-2 (FILTER BALANCE to the far right).
When you set the FILTER BALANCE pot to the
center position (12 o’clock) - as we mentioned
before - the two filters are routed in series,
which means they respond as if they were a sin-
gle filter with 6 poles and consequently a great
deal of slope. This is why the input signal is
trimmed substantially when you set the pot to
this position.

Experiment with the diverse FILTER BALANCE
positions to get a feel for the different degrees
of slope. Rotate the Cutoff pot or activate the
filter envelope (for both filters!) to hear the filters
in action.

The Cutoff 2 pot is a special feature: It controls
the cutoff frequency of the second filter, but is
subordinate to the Cutoff pot located above it.

FILTER BALANCE

CUTOFF

RESONANCE

ENV AMOUNT

CUTOFF 2

SELECT

MODE

FILT 1

FILT 2

EDIT

FILT 2

FILT 1