Rocktron PC Preamp GIS - Manual (Page 12)

25
Operation
This means that if a signal is present at the input which consists of
primarily bass components, the dynamic filter will reduce mid or high
band noise. If no mid or high band information is present, the filter will
close down to a pre-set cut-off point of 1kHz (allowing only frequencies
of 1kHz and below to pass). However, if the input signal has high
frequency components present, the dynamic filter will open fully to pass
the signal and eliminate the possibility of a loss of high end frequency
response.
Dynamic Filtering
Dynamic filtering is achieved by dynamically-controlling a low pass
filter which opens and closes the bandwidth of the output signal
dependent upon the amount of mid and high band information present
in the input signal. The filter bandwidth will only open far enough to
pass the highest frequency information in the input signal, thus
reducing the noise above it.
For example, if the highest frequency present in the input signal is
8kHz, the filter will open to pass up to 8kHz while the noise from 8kHz
to 20kHz would be reduced. If a signal with frequency components up
to 20kHz appears at the input, the dynamic filter will open to its full
extreme (40kHz).
About HUSH noise Reduction