MRD 5800 – User Manual
Page 110 (116)
Audio Output Settings
The digital audio services may be set to PCM (AES) or Pass-through (AES data) as an
output. This applies to all available sources. The PCM setting will decode and
automatically down mix an AC-3 or Dolby Digital Plus stream to two channels of AES
audio. Pass-through simply passes thru the Dolby AC-3 data in an AES stream to be
decoded by an external decoder such as the Dolby 568. Be aware the Dolby DP-568 is
a professional decoder and always has a decoding latency of 32 msec. The older Dolby
DP-564 has both professional and consumer modes of operation. If it identifies the
Pro/Consumer ID bit as Professional, the latency will always be 32 msec. If it identifies
the Pro/Consumer bit as Consumer, the latency will vary according to the format. Check
the DP-564 manual for the actual latency values for Consumer mode. The analog
channels can be assigned to any of the digital sources. The analog gain may be
adjusted for the desired level. The gain setting does not affect the level of either the
embedded audio or the digital services. A setting of +4 dBu provides an output of +4
dBu for a digital signal level of -20 dBFS. To check the audio output level, place the
audio setup in Custom1 mode, down mix set to Lo/Ro, and the Dynamic Range
disabled. This will remove any signal processing in the down mix. Set the digital service
output being measured to PCM. A test stream of -20dBFS will output from the digital
services as -20dBFS. If the analog channels are set to a gain setting of +4 dBu, the
output should be +4 dBu plus or minus 0.5 dBu. The analog output level can be set in
increments of 0.5 dBu from -10 dBu to +4 dBu referenced to a -20 dBFS digital input
level. When you are setting the output levels it is suggested that an AC-3 stereo tone
(2.0) be used as the source. Do not use a Dolby AC-3 5.1 tone source as your test
signal. The five channels will down mix to a different level structure than a stereo signal
depending on the down mix setting.
Downmix Reference Table
The following table is applicable for MPEG Audio (Mono and Stereo), Dolby Digital
(Mono, Stereo and 5.1), Dolby Digital Plus (Mono, Stereo and 5.1) and AAC (Mono,
Stereo and 5.1).
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