User manual

SETUP OF DISCRETE (L & R) AUDIO OUTPUT ENG
Page 45
23.4 ANALOG OUTPUT PRE-EMPHASIS
The XLRs analog output is intended for applications requiring discrete L/R processed audio. The frequency characteristic
can follow a selected pre-emphasis curve, with or without subsequent de-emphasis. The factory-default setting is with
pre-emphasis engaged, accordingly to the destination country (50 or 75 uSec).
Whenever de-emphatization mode is set (ref to the EXTERNAL mode here below), the analog output provides a signal
with a flat frequency characteristic, but with an output ceiling that follows the inverse of the pre-emphasis curve. Thus, if
the signal is again pre-emphasized in an external stereo generator or FM exciter, the transmitted signal will have proper
pre-emphasis and spectral protection.
NOTE: The processor generates two types of pre-emphasis: dynamic and fixed. The former may vary in relation to the
modulation peak, thereby considerably increasing the average modulation within the maximum deviation of 75KHz, while
the latter is fixed at 50 or 75uSec depending on the country in which it is used. If necessary, the latter may be removed
from the analog audio outputs, while the first is always present to ensure proper modulation at all times.
In summary, the following pre-emphasis settings are available:
75uSec External
Flat Response on the analog XLR output, requires external pre-emphatization of 75 uSec**
75uSec Internal
75 uSec pre-emphasized analog XLR output **
50uSec External
Flat Response on the analog XLR output, requires external pre-emphatization of 50 uSec**
50uSec Internal
50 uSec pre-emphasized analog XLR output **
** The
pre-emph.off LED on the front panel glows when the External option is set.
To set the proper pre-emphasis mode:
DEFAULT SCREEN
OUTPUT CALIBRATION menu
PREEMPHASIS page
23.5 OUTPUT PRE-EMPHASIS FOR THE FM VERSION ONLY:
If, for some reason, the unit is to be operated at a preemphasis/de-emphasis which are different to those as supplied,
in addition to the menu setting,
you need to open the top cover and set properly the jumpers CN 17 and CN 18 on the
outside of the I/O MPX board (left board) outward (see picture below)
Only one
pre-emphasis must be kept active in a transmitting chain. It is highly recommended to use
the pre-emphasis within the processor and turn off the one generated by external TX or MPX
Coders.
The processor’s pre-emphasis may be disabled on the analog audio outputs, but NOT on the MPX
output, which remains 50 or 75 uSec pre-emphasized at all times.
- European countries use a pre-emphasis time of 50 uSec.