Omnia Omnia-6EX, Инструкция по установке и эксплуатации

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Omnia-6ex Use and Operation Manual – V: 1.20
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When using the AES/EBU outputs to drive a digital STL or exciter, your Omnia-6EX’s sampling rates must be set
to match the lowest internal operating sampling rate used in any device which follows the Omnia-6 in the audio
chain. You will find these options in the Output Menu; available selections are 32kHz, 44.1kHz, 48kHz, and 96kHz.
Failure to select the proper digital output sampling rate can result in generation of overshoots.
Pre-Emphasis: Where To Insert?
Most digital exciters can generate pre-emphasis within their DSP stereo generator. This is unnecessary when using
an Omnia-6EX, which provides not only the proper pre-emphasis for any region in the world, but maintains
excellent peak control of the pre-emphasized signal so that no overshoots occur. Using pre-emphasis in the digital
exciter instead of that built into your Omnia-6 will result in degradation of performance. Here is some background in
the context of operating in a complete digital environment:
•
Most exciter manufactures recommend the use of their own pre-emphasis network. If this is done, incoming
audio data from the processor must be de-emphasized before it reaches the exciter. Why perform the
emphasis function twice? Also, and more importantly, if the pre-emphasis phase delay is not exactly the
same as the previous de-emphasis in the processor, overshoots will occur. Therefore, it is far more
advantageous to employ pre-emphasis only once—in the Omnia-6EX—and set the exciter to accept a flat
input, which greatly reduces the chance of overshoots being generated. The Omnia-6EX should always be
the standard!
•
We understand why the exciter manufacturers provide these pre-emphasis options; it has to do with digital
codec STLs. Research has shown that pre-emphasized audio routed through a codec is not very friendly
sounding. Hence the de-emphasis in the processor, and second pre-emphasis in the exciter. This is, in our
opinion, a poor solution to the problem. If you must use a codec STL, locate the processor at the transmitter.
Doing so completely eliminates any pre-emphasis/codec abnormalities in the processed audio, and also
allows the processor to have the best possible electrical coupling to the exciter (be it analog or digital).
Hopefully this discussion has served to illuminate some of the issues involved in creating an all-digital transmission
path. Should you experience any problems with overshoot or added distortion after this system is in place, you
should look to the function of the digital exciter and its stereo encoder. As a reference, you can easily make signal
comparisons with the analog outputs from the Omnia-6EX system, especially the composite output. Viewing the
signal on an oscilloscope should reveal that the output is well controlled, with no overshoots, providing a clean
baseband spectrum.