BSS Audio FDS366T OMNIDRIVE User Manual page 24

8.0 Dynamic Equalisation
What is DEQ?
Dynamic EQ boost at -15dB threshold
Dynamic EQ cut at -15dB threshold
The BSS DPR-901 Analogue Dynamic Equaliser was a revolutionary way of
dealing with equalisation, and was made possible by the subtractive
progressive knee technique developed for the industry-standard DPR-402
Analogue Compressor. The very same techniques are used in the FDS-366T to
give you dynamic control of equalisation, or indeed for conventional full-range
compression on every input and every output.
The compressor used in the FDS-366T Dynamic Equaliser uses the audibly
transparent 'subtractive VCA' (Voltage Controlled Amplifier) technology used
in all other BSS compressors, and results in substantially better performance
than other methods. There is clearly no VCA in use in the FDS-366T, as it is a
digital device, but the DSP (Digital Signal Processing) models the effect using
algorithms developed by our crack team of audio systems experts.
The subtractive 'VCA' also allows the realisation of a completely different type
of compression that BSS have named parametric compression. This enables
selective compression to be applied to only certain frequencies in a signal, as
displayed by a conventional looking parametric filter control window. When
the selected frequencies are encountered, the Dynamic Equaliser starts to
compress only those signals at a rate determined by the ratio and threshold
controls.
The Dynamic Equaliser operates in two very different ways depending on
whether the parametric equaliser is set to boost or cut:
In boost mode, the parametric equaliser is allowed to impose its
response on the signal when below threshold, but the effect of the
equaliser is 'flattened out' as the signal starts to exceed threshold.
In cut mode however, the equaliser only has effect above threshold, and
is flattened out as the signal reduces below threshold.
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FDS-366T