Aphex Studio Dominator 700 - Page 29

7.3 Model 704 -With Pre/De-Emphasis and Lowpass Filter
This card contains the circuits of Model 702 described
above (including the required limiter modifications) with the
addition of an overshoot corrected 15KHz lowpass filter for FM
broadcasting or other bandwith restricted applications.
The pre-emphasized studio Dominator with lowpass filter
limits spectral energy according to the amplitude constraints of
the pre-emphasis curve to allow maximum dynamic range
utilization of the pre-emphasized audio channel. Further, a
"brick-wall" filter sweeps away all signficant energy which may
be present outside the 15KHz upper frequency limit. Because of
the multiband limiting and automatic limiting threshold
features, sonic effects of the limiter are greatly diminished.
A very transparent "unprocessed" sound can be obtained while
gaining significant signal-to-noise improvements and complete
protection from common effects such as sibilance breakup,
main-to-sub crosstalk, etc.
The Studio Dominator's lowpass filter is a high quality
ninth-order eliptical active filter type which is flat in
frequency response within O.2dB to 15KHz but is down at least
90dB at the 19KHz pilot frequency. A modified state-variable
topology is used to attain a sonically excellent filter having
very high stability with low noise and distortion. Out-at-band
rejection is 60dB or greater above 19KHz. Phase matching is
excellent between left and right channels throughout the
passband and into the reject band.
The lowpass filter is inserted after all limiting. This
enables the Studio Dominator to produce very well band li~ited
extremely accurate peak modulation having high dynamic stereo
separation (low main to sub crossstalk) in composite FM.
NOTE: The audio output from a Studio Dominator equipp~d with
pre-emphasis and lowpass filters is suitable for direct
connection to an FM stereo generator.
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