Access virus os2 Manuale Utente
9
Now locate the FILT 1 MODE switch which is also located in the FILTERS section. It enables you to
select a filter operating mode from the four available options:
select a filter operating mode from the four available options:
•
LP
: the low pass filter we have just discussed.
•
HP
: the high pass filter which works in the opposite manner of the low pass filter: It suppresses the
lower frequencies in a signal and lets the higher frequencies pass.
•
BP
: the band pass filter which suppresses both ends of the tonal spectrum and allows only a
narrowly defined bandwidth of the original sound to pass.
•
BS
: The band stop filter, band reject filter or notch filter which works in the opposite manner of the
band
pass filter. It allows all of the frequencies of a signal except for a narrow frequency band
around the cutoff to pass. The term „notch“ is fairly descriptive; you might say this filter chops a
notch out of the sound spectrum.
notch out of the sound spectrum.
Now activate the different operating modes and rotate the CUTOFF pot to get a feel for the way each
filtering option works.
filtering option works.
Along with the CUTOFF pot, the RESONANCE pot is the most important control feature of a filter. The
filter resonance increases the volume of the frequencies located near the cutoff frequencies and
suppresses the more remote frequencies. This sound shaping feature has a striking effect - especially
when used in conjunction with the low pass filter: it produces a nasal or honking type of tone which
increases as you turn the resonance up. Experiment by varying the RESONANCE setting in the different
operating modes in conjunction with different CUTOFF settings. You will find the effect that the
RESONANCE pot achieves is markedly different for the band stop filter in comparison to the effect it has
on the other filter types: as the resonance increases, the bandwidth of the notch decreases; in other
words more frequencies on both sides of the filter frequency are allowed to pass.
filter resonance increases the volume of the frequencies located near the cutoff frequencies and
suppresses the more remote frequencies. This sound shaping feature has a striking effect - especially
when used in conjunction with the low pass filter: it produces a nasal or honking type of tone which
increases as you turn the resonance up. Experiment by varying the RESONANCE setting in the different
operating modes in conjunction with different CUTOFF settings. You will find the effect that the
RESONANCE pot achieves is markedly different for the band stop filter in comparison to the effect it has
on the other filter types: as the resonance increases, the bandwidth of the notch decreases; in other
words more frequencies on both sides of the filter frequency are allowed to pass.
Filter Modulation
Of course we don’t want to require you to execute every sound modification manually by twiddling pots.
All kinds of sound modifications in the Virus can be executed automatically much in the way of your
previous experiments with the volume controls: The amplifier envelope can be described as a variable
curve which, depending on the type and duration of attack, hold and release data, automatically
influences (turns it up or down) an imaginary volume pot.
All kinds of sound modifications in the Virus can be executed automatically much in the way of your
previous experiments with the volume controls: The amplifier envelope can be described as a variable
curve which, depending on the type and duration of attack, hold and release data, automatically
influences (turns it up or down) an imaginary volume pot.
Similar procedures are applicable to the filter frequencies. The FILTERS section features its own
envelope, the structure of which is identical to the amplifier envelope, located directly above the
amplifier envelope on the control feature panel. Much like the amplifier envelope, the filter envelope
automatically „rotates“ the CUTOFF pot.
envelope, the structure of which is identical to the amplifier envelope, located directly above the
amplifier envelope on the control feature panel. Much like the amplifier envelope, the filter envelope
automatically „rotates“ the CUTOFF pot.
However there is one significant difference between the two envelopes. With the amplifier envelope, you
are always dealing with an initial volume level of 0 because of course you want absolute silence prior to
the beginning of a note. After the RELEASE phase, it is again highly desirable that your box is silent. With
the filter envelope, the situation is somewhat different: It always starts at the CUTOFF value that you
are always dealing with an initial volume level of 0 because of course you want absolute silence prior to
the beginning of a note. After the RELEASE phase, it is again highly desirable that your box is silent. With
the filter envelope, the situation is somewhat different: It always starts at the CUTOFF value that you