16
Dolby Digital
Dolby Digital (earlier called AC-3)
delivers five discreet full-range
channels (left front, center, right front,
left surround and right surround) plus a
separate Low Frequency Effects (LFE)
channel.
Many soundtracks on the latest
generation laser discs, DVDs and High
Definition Television (HDTV), are
encoded with Dolby Digital technol-
ogy.
When a 5.1 channel Dolby Digital
program source is playing, such as
from a Creative PC-DVD player, the
Dolby Digital indicator light will
illuminate automatically.
Note: Not every section of a DVD
will be 5.1-channel encoded. On many
DVDs, only the main movie program
will be available in 5.1 channel sound.
Other supporting chapters (like a
“Director’s Comment” section) may be
in stereo or mono. These sections will
not light the Dolby Digital indicator
even though the sound will be properly
reproduced by the DTT2500 Digital.
Dolby Pro Logic
Dolby Surround is an earlier
surround sound standard which is
decoded with a Pro Logic processor in
the DTT2500 Digital. The Pro Logic
steering circuitry derives separate
center and rear channels from encoded
stereo program sources.
Pro Logic processing provides a
convincing movie soundfield when the
material is specifically encoded for
Dolby Surround. Most older stereo
movie soundtracks will only be
encoded for Dolby Surround, even
though the program source may be a
DVD’s digital output. Most DVDs
containing Dolby Surround program
material will cause both the Dolby
Digital and Digital Pro Logic lights to
illuminate. DTT2500 Digital will
decode these digitally transferred
Dolby Surround programs through the
digital Pro Logic decoder automatically.
When listening to DVD movies with
5.1 channel Dolby Digital sound, be
sure to listen only to the digital program
source. You can insure this by:
1. making sure your DVD
player’s stereo downmix is
not sent to your soundcard. For
example, disconnect any cable
link between the cards.
2. making sure all four CMSS
indicator lights are off
(MUSIC, MOVIE,FOURPOINT
and STEREO)
3. muting the “CD” input of
your computer’s software mixer/
volume control application.
When playing a DVD game with a
mix of Dolby Digital 5.1 sound (a
digital signal at the SPDIF input) and
soundcard wavetable output (a signal at
the analog input), be sure to engage the
FOURPOINT mode in the CMSS settings.
CD-ROMs and CD’s with Dolby
Surround encoding will feature
the Dolby Surround logo at the
beginning of the program or on the
packaging. Process these programs
by making sure all CMSS indicator
lights are off and selecting the Pro
Logic Analog Input setting of the
Surround Mode button.
CD-ROM’s
and CD’s with Dolby Surround
encoding will feature the Dolby
Surround logo at the beginning of
the program or on the packaging.
Process these programs by
making sure all CMSS indicator
lights are off and selecting the Pro
Logic Analog Input setting of the
Support Mode button. Using this
Analog Pro Logic Mode to decode
Dolby Surround program materia;
at the Digital DIN input.
Do not select a Pro Logic decoding
mode if the program material is not
encoded for Dolby Surround.
Excessive center channel output will
result, and most stereo effect will be
lost. Use CMSS “Movie” or “Music”
modes to upmix stereo programs to a
realistic 5.1 channel sound field.
Surround Reference
