Filter Introduction
Once the audio signal leaves the mixer, it is sent to the
filters. The Blofeld has two independent filter units, each
with its own individual settings. The signal flow in the
filters can be controlled via the Routing function. The
filters are components that have significant influence on
the Blofeld’s sound characteristics.
For a detailed description of the different filter types that
are available in the Blofeld, see the section “Filter Types”
on page 78. For now, we’ll explain the basic function of a
filter discussing the type used most commonly in
synthesizers: the low pass filter.
The low pass filter type dampens frequencies that lie
above a specified cutoff frequency. Frequencies below
this threshold are hardly affected. The frequency below
the cutoff point is called the pass band range, the
frequencies above are called the stop band range. The
Blofeld’s filter dampens frequencies in the stop band with
a certain slope. The slope can be 12dB or 24dB per
octave. This means that the level of a frequency that lies
an octave above the cutoff point will be 12dB or 24dB
less than those frequencies of the signal that fall into the
pass band. The following picture shows the basic
principle of a low pass filter:
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