Operation Manual

46 Parameters
6.3 The Equalizer Module
The EQ module provides equalization over the low, mid, and high frequency bands and is switched
on or off using the On button. It is composed of a low-cut filter, a low shelf filter, a peak filter, and
a high shelf filter in series.
The low-cut (or high-pass) filter is used to
remove from the output sound of the instru-
ment frequency components below the cut-off
frequency. The cut-off frequency of the fil-
ter is increased by turning the knob clockwise.
when this knob is in its leftmost position, the
filter has no effect on the sound.
The functioning of the low shelf filter is illustrated in Figure 21. The filter applies a gain factor
to frequency components located below a cutoff frequency while leaving those above unchanged.
The cutoff frequency of this filter is fixed and located at 500 Hz. The amount of gain is controlled
with the Low knob. In its center position there is no attenuation (0 dB). Turning it clockwise will
boost the amplitude of low-frequencies will turning it anti-clockwise will reduce it.
The high frequency content of the signal is controlled with a high shelf filter that works in
the opposite manner as the low shelf filter as illustrated in Figure 21. The filter will multiply a
gain factor to components located above a cutoff frequency while leaving those below unchanged.
The cutoff frequency of this filter is located at 3 KHz and the amplitude of the high frequencies is
controlled using the Hign knob which works similarly to the Low knob.
Amplitude (dB)
0dB
Freq Frequency (Hz)
Amplitude (dB)
0dB
Frequency (Hz)Freq
Gain = −30 dB
Gain = 10 dB
Gain = 20 dB
Gain = 30 dB Gain = 30 dB
Gain = 20 dB
Gain = 10 dB
Gain = −30 dB
Figure 21: Low and high shelf filters.
The mid frequency content of the signal is adjusted using a peak filter as illustrated in Fig-
ure 22. The filter applies a gain factor to frequency components in a band located around the cutoff
frequency of the filter. The cutoff frequency of the filter is adjusted with the Freq knob while the
gain coefficient is varied with the Mid knob. When the Mid knob is in its center position there is no
attenuation (0 dB). Turning it clockwise will boost the amplitude of low-frequencies will turning it
anti-clockwise will reduce it.