User Manual

ALF-DSP 88-U
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The equalizer has the following control parameters:
Type: Parametric EQ is the default setting. High and low shelf filters and high and low pass filters can also be
selected. Each kind of filter has different forms to achieve different functions.
High and Low Pass Filter: The reference frequency of a pass-type filter is called the cut-off frequency. Pass-type
filters allow the frequencies on one side of the cut-off frequency to fully pass the filter; in the meantime, the
frequencies on the other side of the cut-off frequency are attenuated at a constant dB ratio per frequency octave.
High pass filters allow the frequencies above the cut-off frequency to pass and filter the frequencies below the cut-
off frequency. To the contrary, low pass filters allow the frequencies below the cut-off frequency to pass and filter
the frequencies above the cut-off frequency.
High and Low Shelf Filter: High shelf filter means that the gain increases or attenuates for the frequencies above
the set frequency. Low shelf filter means that the gain increases or attenuates for the frequencies below the set
frequency. The set frequency is not 3dB cut-off frequency but refers to the center of the failing edge or rising edge
of the filter. Q value affects the peak and has a mathematical relation with the peak.
Frequency (Hz): Refers to the center frequency of the filter.
Gain (dB): Refers to the increased or attenuated decibel value of the gain at the center frequency.
Q: It refers to the quality factor of a filter. The adjustable range of the Q value is 0.02-50.
When the filter is set as a parametric EQ filter, Q value refers to the width of the bell-shaped frequency response
curve on both sides of the cut-off frequency.
When the filter is a high and low shelf filter or a high and low pass filter, if Q>0.707, there will be peaks in the filter
responses. If Q<0.707, the slope will become flatter, and the roll-off will occur in advance.
Each segment of the equalizer has a switch, which is used to turn on or turn off the corresponding segment. Wh en
turned off, that frequency parameter settings are disabled.
The equalizer has a master switch, which is used to enable or disable the whole module.
3.4.6 Graphic Equalizer
By using a constant Q-value, each frequency point is equipped with a push-pull potentiometer. The bandwidth
of the filter remains unchanged regardless of if the frequency is raised or attenuated. The common
professional graphic equalizer is to divide 20 Hz~20 kHz signals into 10, 15, 27 or 31 bands / frequencies to
adjust.
The graphical equalizer has 10, 15 and 31 band options