Operation
Note that the Dolby Digital or DTS modes may only be selected when a digital input is in use. In addition, when a digital source is present, the AVR will automatically select and switch to the correct mode (Dolby Digital or DTS), regardless of the mode that has been previously selected. For more information on selecting digital sources, see the following section of this manual.
When the 6-Channel/8-Channel direct inputs are in use there is no surround processing, as these inputs take the analog output signals from an optional, external DVD-Audio or SACD player, or another source device and carry them straight through to the volume control.
To listen to a program in traditional two-channel stereo, using the front left and front right speakers only (plus the subwoofer, if installed and configured), press the Stereo Button 5
until SURR OFF appears in the Main Information Display ˜.
Digital Audio Playback
Digital audio is a major advancement over older analog surround processing systems such as Dolby Pro Logic. It delivers five or six discrete channels: left front, center, right front, left sur- round and right surround and with DTS ES (see below) even surround back (with identical signals for left and right). Each channel reproduces full frequency range (20Hz to 20kHz) and offers dra- matically improved dynamic range and significant improvements to signal-to-noise ratios. In addi- tion, digital systems have the capability to deliver an additional channel that is specifically devoted to low-frequency information. This is the “.1” channel referred to when you see these systems described as “5.1,” “6.1” or “7.1”. The bass channel is separate from the other channels, but since it is intentionally bandwidth-limited, sound designers have given it that unique designation.
Dolby Digital
Dolby Digital (originally known as AC-3®) is a standard part of DVD, and is available on specially encoded LD discs and satellite broadcasts and it is a part of the new high- definition television (HDTV) system.
Note that an optional, external RF demodulator is required to use the AVR to listen to the Dolby Digital sound tracks available on laser discs.
Connect the RF output of the LD player to the demodulator and then connect the digital output of the demodulator to the Optical or Coaxial
inputs *Ó of the AVR. No demodulator is required for use with DVD players or DTS- encoded laser discs.
In order to provide maximum playback compatibility with DVDs, the AVR 645 receiver will always default first to the playback mode embedded in a disc’s digital “flag” information. For Dolby Digital discs, the following playback modes are initially selected after the AVR locks to the incoming digital audio data stream to identify the selected:
•When a 5.1 audio stream is detected, the Dolby Digital 5.1 format will be selected, regardless of the number of speakers in your system, in compliance with Dolby Laboratories licensing requirements.
•When a disc with the Dolby Digital EX format flag is played, your system will automatically switch to the EX mode when seven main channel speakers are available.
•When a disc with Dolby Digital data, but only
2.0audio is detected, the default mode is Dolby Digital with Pro Logic II post-processing when you have a 5.1 speaker system, or Dolby Digital with Pro Logic IIx post-processing when you have a 7.1 speaker system.
•Depending on the number of speaker channels available in your system, once the AVR locks to the digital signal, you may select any surround mode or post-processing option that is available, based on the incoming data stream’s possible restrictions and the number of speak- ers in your system. For example, when a 5.1 or
2.0audio stream is in use, you may select alternate postprocessing such as Logic 7/7- Channel Movie Mode post-processing to create the rear surrounds in 7.1 speaker systems.
DTS
DTS is another digital audio system that is capable of delivering 5.1, 6.1 or 7.1 audio. Although both DTS and Dolby Digital are digital, they use different methods of encoding the signals, and thus they require different decoding circuits to convert the digital signals back to analog.
DTS-encoded sound tracks are available on select DVD and LD discs, as well as on special audio- only DTS CDs. You may use any LD, DVD or CD player equipped with a digital output to play DTS-encoded special audio-only CDs with the AVR, but DTS-LDs can be played on LD players and DTS-DVDs on DVD players only. All that is required is to connect the player’s digital output to either the Optical or Coaxial input on the
rear panel | or front panel *Ó. |
In order to listen to DVDs encoded with DTS sound tracks, the DVD player must be compatible with the DTS signal as indicated by a DTS logo on the player’s front panel. Note that early DVD players may not be able to play DTS- encoded DVDs. This does not indicate a problem with the AVR, as some players cannot pass the DTS signal
through to the digital outputs. If you are in doubt as to the capability of your DVD player to handle DTS DVDs, consult the player’s owner’s manual.
Please note that some DVD players are shipped with their output set for Dolby Digital only. To insure that DTS data is being sent to the AVR, please check the setup menu system on your DVD player to make certain that DTS data output is enabled.
PCM Audio Playback
PCM (Pulse Code Modulation) is the non- compressed digital audio system used for compact discs, Non-Dolby Digital/DTS Laserdiscs and some special PCM encoded DVDs. The digital circuits in the AVR are capable of high quality digital-to-analog decoding, and they may be connected 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 or the front panel Digital Inputs *Ó.
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 Û G and then use the ⁄ / ¤ buttons E on the remote, or the Selector buttons 7$ on the front panel, until the desired choice appears in the Lower Display Line ˜, then press the Set button @ F to confirm the choice.
In most cases this will be 48 KHZ, though in the case of specially mastered, high-resolution audio discs you will see a 96 KHZ indication.
The PCM 48 KHZ indication will also appear when modes or inputs are changed for analog sources. In those cases the system is telling you the sampling frequency used internally at the output of the analog-to-digital converters that change the incoming signal from a VCR, tape deck, the tuner, or other ana-log source to digital.
During PCM playback the unit automatically will turn to the default surround mode or to the LOGIC 7 mode but you also may select any surround mode except Dolby Digital or DTS.
