VIRUS Owner’s Manual
14
The First Oscillator
To this point, we have turned our attention exclusively to sound-shaping functions and have always
started with the same basic material: a so-called sawtooth wave. This waveshape is especially well-suited
as a neutral starting point as it contains all of the so-called natural scale of overtones, which give the
filter plenty of quality material to work with.
The filters, with the exception of a notch filter or band stop (BS), trim the far reaches of the tonal
spectrum, so for instance a signal sounds muddier after it has been routed through a low pass filter. You
can well imagine that this type of sound modification is substantial but insufficient for shaping more
subtle differences in tone. For instance the tone of a trumpet differs significantly from that of a
saxophone even though no one would seriously claim that either of the instruments has a muddier tone
than the other.
What you need is a sound-shaping option for the portion of a signal that a filter allows to pass. And of
course you also need a tool for determining the pitch of a signal. In synthesizers, both of these tasks are
executed by oscillators. They oscillate at a variable pitch that can be modulated and they also generate
different waveshapes which give the filters a wider variety of material to work with.
The Virus is equipped with two main oscillators and a so-called suboscillator. We will first take a look at
Oscillator 1, which is the oscillator you have already heard in action during your experiments thus far.
Dial in the same basic sound that you started with at the very beginning. Now modify the amplifier
envelope so you are working with a less grating sound, but hold back on any other filter or saturation
modifications so you can hear the purest oscillator signal possible.
Locate the section labeled "1", it is bordered off in a separate area at the far left of the section labeled
OSCILLATORS. No check out the two pots labeled SHAPE and WAVE SEL/PW. These enable you
determine the waveshape and consequently the tonal spectrum of Oscillator 1.
In the sound program,
SHAPE
is preset to the center position (12 o’clock), which is equivalent to a
value of 64. On the pot, this position is identified via a graphic depiction of a sawtooth wave. You can
definitely see why this waveshape bears the name „sawtooth.“ Press and hold a key and slowly turn the
pot clockwise. You should be able to hear how the tone becomes increasingly more hollow-sounding.
You might say this effect thins the sound out, but in any case, the entire tonal spectrum is affected by an
equal measure, which is an audio result filters are unable to achieve.
The waveshape that is audible when you turn the SHAPE pot to the far right is a so-called pulse wave.
The graphical representation of this waveshape on the control panel gives you a good idea of its
appearance. It is unique because the duration of the negative pulse is equal to the duration of the
positive pulse: It has a so-called pulse width of 50%. The tone of a pulse wave is different to that of a
sawtooth wave because it does not contain all overtones in the natural overtone scale, only the odd-
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