Omnia-6fm User's Manual v1.00 - bei Thum + Mahr!

Pre-Emphasis
For the transmission side of FM broadcasting, some form of high-frequency boost, or pre-emphasis is used.
The most commonly used values of pre-emphasis are 50 and 75 µs (microseconds). For North and South
America, 75 µs is used. In Europe, Australia and New Zealand, 50 µs is employed. The factory default preemphasis
setting is 75 µs. The pre-emphasis selection affects the operation of the audio processing and is
applied to the composite, discrete, and digital outputs. The pre-emphasized signal at the Left/Right and
digital outputs can be restored to flat, if needed, by the De-Emphasis parameter selection.
To set the Pre-Emphasis, rotate the jog-wheel to highlight one of the three choices: Off, 50 µs or 75 µs.
Click the jog-wheel to set the pre-emphasis selection.
Note: Normally, the Off selection under the Pre-emphasis options would not be used in FM transmission
applications, but is provided in instances where processing of a flat signal is desired. One example would
be when preprocessing prior to a satellite uplink in distributed radio networks.
Output
Output Submenu
There are four settings under this menu
item:
• Peak Output Level
• De-Emphasis
• Output Sample Rate
• ITU BS-412 Multiplex Power
Limiter
Peak Output Level
The left/right peak output level adjustment is done in a similar manner as the setting of the input levels.
These level settings take place in the digital domain and before any D/A converters. Therefore, the output
level settings affect the digital (AES/EBU) output, and the analog outputs including the headphones. The
control range is from 0 dBu (-22 dBFS) to +22 dBu (0dBFS) peak output level. This level is normally set
to the maximum input level, or just below it, of the device that the Omnia-6 is driving (STL, transmitter,
etc.).
Omnia 6 Use and Installation Guide – Version 1.00a
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