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FM-531HD / May 2013
F M - 5 3 1 H D G U R U G U I
Important Gain Reduction Display Metering Notes:
• The SST and five band AGC utilize a meter scale that goes from 0dB at the top
to ‑30dB at the bottom.
• The 31‑band limiter, main FM and MPX limiter/clippers and BS‑412 algorithm
utilize a meter scale that goes from 0dB at the top to ‑15dB at the bottom.
• The VBMS meter does not need nor does it have a calibrated scale.
The 31‑band limiter does not need to do much work to gain its advantages. In fact,
less is more. Gain reduction deeper than 5‑6dB is not only unnecessary, but doesn’t
generate any further gains in loudness. Unlike the limiters in all other broadcast
audio processors, when 6dB, 10dB, or even more is required in order to generate
consistency and competitive loudness, the 31‑band limiter’s best sound quality and
loudness results when its bands are just being “tickled.”
Analysis Menu
The FM‑531HD is equipped with extensive processing
analysis features that show what the processing is doing and
by how much and when. The Guru GUI has a drop down
menu where the analysis to be viewed may be selected.
There are six options in this drop down menu:
•
FFT
– Displays the spectral output of the FM or HD
processing paths after processing. The FM display
includes any pre-emphasis being used in order to
present an accurate view of the signal actually being
sent to the transmitter by the FM‑531HD.
•
O-Scope
– Displays the audio waveforms at the output
of the FM or HD processing chains.
•
E vs F
– Displays the measured
RMS Loudness
within each of the 31 limiter
bands.
•
3-D Plot
– A three‑dimensional plot of the audio, after processing, which displays
signal amplitude versus frequency versus time. The display has a ten second
historical window depth allowing some historical perspective about the FM or
HD audio after processing.
•
SDR™
– Spectral Dynamic Range™ (a Wheatstone exclusive). This display
shows the amount of dynamic range
remaining in each of the 31 FM or HD
limiter bands, after processing.
•
A-Clip
– This is FM‑531HD’s final FM clipper activity display (another Wheat
-
stone exclusive) that shows
where in the audio spectrum distortion products are
being detected and reduced and by how much.
A detailed explanation of each analysis type follows.
FFT
This display shows a Fast Fourier Transform of the audio spectrum after process
-
ing has been applied by the final FM clipper or HD limiter. The FFT display’s high
resolution is useful for locating where in the audio spectrum certain signals are heard.
Summary of Contents for FM-531 HD
Page 2: ...Technical Manual Wheatstone Corporation May 2013 FM HD Digital Audio Processor FM 531hd...
Page 122: ...page A 2 FM 531HD May 2013 A P P E N D I C E S Appendix A General Specifications A 3 Contents...
Page 128: ...page A 8 FM 531HD May 2013 A P P E N D I C E S Appendix B FM 531HD GPI Interface A 9 Contents...
