Omnia-6Ex Connections; Output Connection Options (Fm Mode); Interfacing With A Digital Stl/ Exciter - Omnia -6EX / EXi Installation And Operation Manual

Omnia-6EX Connections

FM Mode (Conventional Channel) Output Connection Options
Tests have shown that post-processing audio power in the low frequency region is so strong that it may affect the
performance of some exciters. It is imperative that your exciter have a dual speed PLL in the AFC, otherwise it may
unlock. If one of your processing goals includes solid, powerful bass on air, this is an important key point that
cannot be overlooked or loudness will be lost due to inefficient modulation.
Output choices are:
Left/Right Analog: This option is provided for compatibility only, and is the least-recommended choice. The DSP
based digital stereo generator included in your Omnia-6EXprovides superior performance, and should be used
instead of the one provided in the exciter.
Analog Composite: If you don't object to your air chain being partially analog, this option will provide excellent
peak control and sound quality. Be sure to use good quality low capacitance coaxial cables for best performance.
Typical cables may be RG-58 or RG-62 type.
AES/EBU: Selectable sampling rates are provided to minimize overshoots caused by down-sampling in external
equipment. This option, however, cannot make up for potential sonic degradations (see "Interfacing with a Digital
STL and/or Exciter" below).
The typical connection to a digital STL or exciter is through the standard, balanced AES/EBU connection. Using a
shielded 110 ohm digital audio cable with appropriate XLR connectors on each end, connect the processor to the
exciter. Cable length should be as short as possible, and may not exceed 100 meters (328 feet). The exciter input
should be set for flat input, which means that the exciter is not adding any pre-emphasis to the input signal. In the
Omnia-6EX Input menu set the Pre-emphasis "ON" at the correct value for your country. In the Output Menu, set
the De-emphasis option to "OFF". This ensures that output from the processor is now pre-emphasized according to
the standard in use in your country. You will also need to adjust the output levels and Output Sampling Rate in the
Output Menu. Since the digital exciter will be providing the stereo generator function, you must set the Peak Output
Levels in the Output Menu for the proper AES/EBU discrete left/right channel levels, and also set the AES-1
Sample Rate to the actual internal operating sample rate of the exciter. For the AES-2 output, the output sample rate
is set using jumpers on the internal SRC (Sample Rate Converter) board.
Interfacing With A Digital STL and / or Exciter
At the time of this writing, many engineers are proponents of the all-digital broadcast transmission path. However,
there are some key issues, which must be dealt with when implementing all-digital transmission in order to preserve
loudness without sacrificing audio quality. One issue concerns the sampling rate of the audio processor and that of
the exciter. In order for two differently sampled systems to be interfaced in the digital domain, a neat little device
known as the "sample rate converter" is used.
For instance, a device which outputs digital audio data using a 48 kHz (or higher) sampling rate can be converted
down to a lower rate of, say, 32 kHz. Unfortunately, unless spectrum is limited to the Nyquist frequency of the lower
rate, overshoots can be created, robbing you of loudness. Detailed information can be found in the technical papers
"Critical issues and Considerations for an All Digital Transmission Path," "Digital Dynamics Processing: It's All In
The 'Samples!'" and "Digital Broadcast Audio Processing: Finally, The New Frontier" on the Omnia Tech Info web
page at http://www.omniaaudio.com.
Omnia-6ex Use and Operation Manual – V: 1.20
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