22 OPERATION
Operation
PCM Audio Playback
PCM (Pulse Code Modulation) is the non- com-
pressed digital audio system used for compact
discs, Non-Dolby Digital/DTS Laserdiscs and
some special PCM encoded DVDs. The digital cir-
cuits in the AVR 1550 are capable of high quality
digital-to-analog decoding, and they may be con-
nected directly to the digital audio output of your
CD/DVD or LD player (LD only for PCM or DTS
programs, for Dolby Digital laser discs an RF
adapter is needed, see ”Dolby Digital” above).
Connections may be made to either the Optical
or Coaxial inputs
on the rear panel.
To listen to a PCM digital source, first select the
input for the desired source (e.g., CD) to feed its
video signal (if any) to the TV monitor and to
provide its analog audio signal for recording.
Next press the Digital Select button
Ô
F
and then use the
⁄
/
¤
buttons
C
on the
remote, or the Selector buttons
&
on the front
panel, until the desired choice appears in the
Main Information Display
M
, then press the
Enter button
E
on the remote control, or the
Set button on the front
Ó
to confirm the
choice.
When a PCM source is playing, the PCM indica-
tor
A
will light. During PCM playback you may
select any surround mode as described on pages
20 and 21 except Dolby Digital or DTS.
Selecting a Digital Source
To utilize either digital mode you must have
properly connected a digital source to the
AVR 1550. Connect the digital outputs from
DVD players, HDTV receivers, satellite systems or
CD players to the Optical or Coaxial inputs on
the rear panel
.
When playing a digital source such as DVD, first
select its input using the remote or front panel
controls as outlined in this manual in order to
feed its video signal (if any) to the TV monitor
and to provide its analog audio signal for
recording. When the digital input appropriate
with the DVD player is not selected automatical-
ly (due to the input settings made earlier during
the system configuration, see page 14), select
the digital source by pressing the Digital Input
Selector button
F
Ô
and then using the
⁄
/
¤
buttons
C
on the remote or the
Selector buttons
&
on the front panel to
choose any of the OPTICAL or
COAXIAL
inputs, as they appear in the
Main Information Display
M
and Display
Indicators
BE
. When the digital source is
playing, the AVR 1550 will automatically detect
whether it is a multichannel Dolby Digital, DTS
source or a conventional PCM signal, which is
the standard output from CD players.
A Bitstream Indicator
A
will light in the
Main Information Display
*
to confirm that
the digital signal is Dolby Digital, DTS or PCM.
Note that a digital input (e.g. coaxial) remains
associated with any analog input (e.g. DVD) as
soon as it is selected, thus the digital input need
not be re-selected each time the appropriate
input choice (e.g. DVD) is made.
Digital Status Indicators
When a digital source is playing, the AVR 1550
senses the type of bitstream data that is present.
Using this information, the correct surround
mode will automatically be selected. For exam-
ple, DTS bitstreams will cause the unit to switch
to DTS decoding, and Dolby Digital bitstreams
will enable Dolby Digital decoding.When the unit
senses PCM data, from CDs and LDs and some
music DVDs or certain tracks on normal DVDs, it
will allow the appropriate surround mode to be
selected manually. Since the range of available
surround modes depends on the type of digital
data that is present, the AVR 1550 uses a variety
of indicators to let you know what type of signal
is present.This will help you to understand the
choice of modes and the input channels recorded
on the disc.
When a digital source is playing, a Bitstream
Indicator
A
will light to show which type of
signal is playing:
: When the DOLBY D indicator lights, a
Dolby Digital bitstream is being received.
Depending on the audio track selected on the
source player and number of channels on the
disc, different surround modes are possible. Note
that only one channel without subwoofer, called
”1.0” audio, or all five channels with subwoofer
(”5.1” audio) or all steps between can be
recorded on digitally surround encoded audio
tracks (see NOTE below). With all those tracks,
except ”2.0” audio, only the Dolby Digital mode
is available. When the Dolby Digital signal is only
two channel (”2.0”) these two channels (l and r)
often contain Pro Logic surround informations.
With those tracks the AVR 1550 automatically
switches to the Dolby Pro Logic II Movie mode
(in addition to the Dolby Digital mode). When
the D.D. 2.0 signal contains no Pro Logic infor-
mation, the pure Dolby Digital mode will be
selected automatically, but you may also select
any Pro Logic II mode (only Music or Emulation
should be used then).
DTS:When the DTS indicator lights, a DTS
bitstream is being received.When the unit senses
this type of data, only the DTS mode may be
used.
PCM:When the PCM indicator lights, a standard
Pulse Code Modulation, or PCM, signal is being
received.This is the type of digital audio used by
conventional compact disc and laser disc record-
ings. When a PCM bitstream is present, all modes
except Dolby Digital and DTS are available. Note
that the PCM signal format can be selected on
the DVD player with any audio track, even with
Dolby Digital tracks (but not with Dolby Digital
decoding). So, if selected, even ”2.0” D.D. audio
tracks can be played with all surround modes.
In addition to the Bitstream Indicators, the
AVR 1550 features a set of unique channel input
indicators that tell you how many channels of
digital information are being received and if the
digital signal is interrupted.
These indicators are the L/C/R/SL/SR/LFE letters
that are inside the center boxes of the
Speaker/Channel Input Indicators
P
in the
front panel Main Information Display
*
.
When a standard analog stereo or matrix
surround signal is in use, only the “L” and “R”
indicators will light, as analog signals have only
left and right channels, respectively, even
surround recordings, carry surround information
on the left and right channels only.
Digital signals, however, may have one to six
separate channels, depending on the program
material, the method of transmission and the
way in which it was encoded. When a digital
signal is playing, the letters in these indicators
will light in response to the specific signal being
received. It is important to note that although
Dolby Digital, for example, is referred to as a
“5.1” system, not all Dolby Digital DVD or audio
tracks selected on DVD or other Dolby Digital
programs are encoded for 5.1.Thus, it is some-
times normal for a DVD with a Dolby Digital
soundtrack to trigger e.g. only the “L” and “R”
indicators.
Night Mode
A special feature of Dolby Digital is the Night
mode, which enables Dolby Digital input sources
to be played back with full digital intelligibilty
while reducing the maximum peak level and lift-
ing the low levels by
1/4 to 1/3. This prevents
abruptly loud transitions from disturbing others
without reducing the impact of the digital
source. The Night mode is available only when
Dolby Digital mode is selected.
The Night mode may be engaged when a Dolby
Digital DVD is playing by pressing the Night
Button
A
on the remote. Next, press the
⁄
/
¤
buttons
C
to select either the middle range or
full compression versions of the Night mode. To
turn the Night mode off, press the
⁄
/
¤
buttons
C
until the message in the lower third of
the video display and the Main Information
Display
M
reads D-ROFF.
When the Night mode is active, the Night
Mode Indicator
O
will also illuminate.
