User manual

SETUP OF DISCRETE (L & R) AUDIO OUTPUT ENG
Page 47
To enable
the output power limiting:
DEFAULT SCREEN
OUTPUT CALIBRATION menu
POWER LIM(ITER) page
OUTPUT POWER LIMITER
The output power calculation does not take into account the injection values of the Pilot, external RDS
signal and possible SCA signals. The following values are therefore assumed by default in the power
calculation:
Pilot = - 20dB, Rds = - 31.5dB, Preemphasis = 50 uSec, No SCA signals
Whenever RDS or Pilot levels are different from the default ones, the processor has enough adjustment available (Ref.
Adj) on it that allows the processing to be compensated in order to keep the modulated signal within the BS-412 limits.
For instance:
Output mode Limiting threshold
RDS signal not available + 0.25 dBITUref
Mono signal (no Pilot available) +1.0 dBITUref
Mono signal (no Pilot available) + RDS +0.75 dBITUref
For better results, we recommend to use the Equalization Presets 29 and 30 (labeled as ITU), as they
have been especially designed to keep the output power as much constant as possible.
As expected result, the power level will always range by less than 0.5 dBITU in respect of the
reference output level and it will never exceed +1 dBITU ceiling. The other Presets will provide a still
ITU-compatible output, but with power output levels reduced by 0.5 dB.
The graphic shows the performance of the MPX limiter over a 33 minute time period:
This test was done using an audio CD. The dips are due to the pauses between the tracks on the CD; those dips are
thus factored into the average of the measurement.
As can be observed on the graphic, the MPX level never exceeds by more than + 0.5 dB the 0 dBu level limit (this is the
reference level that indicates the 19kHz average power deviation level).
Deviation peaks range between 55Khz and 70Khz depending on the aired audio material.