Audio DSP with AEC, 4-in/4-out analog, 4-in/4-out Dante and USB
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Threshold:
When the signal level is lower than the threshold, the input-to-output ratio is 1:1. When the
signal level is higher than the threshold, the input-to-output ratio changes with the ratio control settings.
The threshold should be set just above the background noise level to avoid amplification of the noise.
Ratio:
Refers to the ratio of the changes in level when the input signal is higher than the threshold.
Target level:
Refers to the target output level. If the signal is higher than the threshold, the controller will compress the signal
proportionally
.
Attack (ms):
Refers to the time required to activate the AGC when the signal is above the threshold.
Release (ms):
Refers to the time required for the gain to be restored when signal is below the threshold
3.3.5 Equalizers
Filter for changing the frequency balance of the signal.
The equalizer has the following control parameters:
Fig.3.6
Equalizer
Type
: Parametric EQ is the default filter type. Additionally, high & low shelf filters and high & low pass filters can be selected.
High & Low Pass Filter:
The high-pass filter will pass through frequencies higher than the set frequency and attenuate the
frequencies below this with a slope of 12dB/octave. Default Q of 0.71 gives a maximally flat amplitude (Butterworth). The low-
pass filter works in a similar way but attenuating above the corner frequency.
High & Low Shelf Filter:
A shelving filter will amplify or attenuate the frequencies above (high shelf) or below (low shelf) the
set frequency by the amount set in the gain parameter.
Frequency (Hz):
Refers to the centre frequency of the filter.
Gain (dB):
Amount of gain or attenuation of the signal at the set frequency.
Q
: Refers to the quality factor of a filter. The adjustable range of Q value is 0.02-50.
For 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 & low shelf filter or a high & low pass filter, if Q>0.707, there will be peaks in the filter responses. If
Q<0.707, the slope will become flatter.
The Q-factor parameter should be used with caution, as a too high value can result in a resonant filter function.
Each segment of the equalizer has a switch, used to turn on or turn off the filter. After being closed, the parameter setting will
not work. The equalizer has a master switch used to enable or disable all filters.
