The First Filter - Access Virus Rack XL User Manual

20
CHAPTER 5
Introduction
automatically influences an imaginary volume
encoder (turns it up or down). At the beginning
of the note, ATTACK controls the rise or rate of
increase to the maximum level. Once the maxi-
mum level is achieved, DECAY determines the
fall or rate of decrease to the SUSTAIN value,
which is infinitely variable between the mini-
mum and maximum levels. The amplifier enve-
lope may remain at this value until the end of
the note, fall towards the minimum level as de-
termined by the variable TIME value, or even ri-
se again towards the maximum level. After the
end of the note, RELEASE controls the fall or
Now we will take a look at a component of a
synthesizer that is generally regarded as the
most important functional unit as it enables dra-
stic sound shaping measures: the filter - or in
the case of the Virus, the two filters.
But first we will concentrate on just one of the
two filters.
Use the UP or DOWN buttons to activate the fil-
ter section FILT. The second encoder knob in
this row is labeled CUTOFF (not to be confused
with CUTOFF 2!). Rotate the encoder to the left
and right and note how the sound becomes
muddier and clearer in response to the direction
in which you turn the encoder. (To ensure this
effect and the following aural experiments are
rate of decrease to the minimum level. Conse-
quently, the control encoders labeled ATTACK,
DECAY, TIME and RELEASE control a speed or
rate, where as SUSTAIN actually controls a le-
vel.
í

THE FIRST FILTER

most pronounced, adjust the amplifier envelope
so that the Virus generates a constant level whi-
le you hold a key down).
This is how a low pass filter works: it suppres-
ses, or in technical jargon, attenuates the higher
frequencies in a signal and allows the lower fre-
quencies through. Think of the CUTOFF enco-
der as a bouncer and the Virus as your pub. You
can tell it which frequencies to let in and which
frequencies to keep out. The frequencies above
the so-called cutoff or filter frequency are sup-
pressed, those below it remain unaffected.
Now we'll look at a parameter that is not assi-
gned a dedicated knob of its own, but can be
dialed up in the display. This type of parameter
may be selected via the PARAMETER buttons
and then adjusted with the VALUE knob or the
VALUE buttons.
Select the FILTER 1 Mode parameter via the
PARAMETER buttons. To do this, make sure
that the display is still in the filter section FILT.
This parameter enables you to select a filter
operating mode from the four available options:
- LOWPASS the low pass filter we have just
discussed.