B&K Reference 21, Owner'S Manual

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4
THE BASICS
The following is intended to familiarize users with common terms and applications of Home Theater equipment.
Sources - your processor can provide audio from its built-in AM/FM tuner. It can also provide limited video from
its on-screen menu system. You will want to connect a number of additional sources (VCR, DVD player, etc.) to
your processor. Your processor is designed to accommodate a wide range of audio and video signals.
The following table lists the most popular home theater media and how the audio information is stored.
Source Media Analog PCM Dolby Digital DTS
Audio Cassette X
Video Cassette X
Laser disc (LD) X X X X
Compact Disc (CD) X X X
Digital Versatile Disc (DVD) X X X
Satellite Broadcast X X
Digital Audio Tape (DAT) X X X X
Digital Compact Cassette (DCC) X (compressed)
Mini disc (MD) X (compressed)
Analog vs. Digital Audio - This refers to the method used to place audio information on the source material and
how they are delivered to your processor from the source. Analog signals exactly represent the sound you will
hear through a continuously varying voltage. Audio and videocassettes are analog recordings and are normally
delivered to your processor over a pair of coaxial audio cables.
Digital signals closely approximate the original audio signals with a set of numbers referred to as a bitstream. CDs
and DVDs are sources of digital audio and are normally connected to your processor through a coaxial or optical
digital cable. There are several different bitstream formats available. The simplest format is called Pulse Code
Modulation (PCM). In PCM, the bitstream directly represents the original 2-channel audio. In Dolby Digital and
DTS (see “Surround Formats” below) bitstreams are modified using a process called compression to squeeze
more information into limited space. DTS squeezes 5.1 channels into the space normally required for two
uncompressed channels, while Dolby Digital squeezes 5.1 channels into about ¼ the space required for two
channels. Your processor automatically detects the bitstream currently being provided from the source and
performs the required decompression and surround processing. If no digital signal is present your processor will
automatically switch to analog processing.
All sounds that you hear from your speakers are analog. Digital signals are automatically converted to analog by
your processor before being output to your the speakers.
If analog signals exactly represent the audio, while digital signals only approximate it, why would I want to use
digital?
All analog sources add some amount of noise and distortion to the audio signal. Additional noise can be picked up
through the cables from the source to your processor. It is impossible for the processor to tell the difference
between the desired signal and the added noise and distortion, so it reproduces both of them. The result is
increased background noise and decreased dynamic range and fidelity. Digital signals are virtually immune to
noise and distortion. The processor can, therefore, reproduce the signal with the greatest possible fidelity. We
recommend you use digital signals wherever possible. Also Dolby Digital and DTS (see “Surround Formats”
below) work only with digital signals.
Audio and Surround Formats - Your source material will be in one of seven possible formats described below.
Monaural (Mono) - This is the oldest audio format available. It contains a single, full range audio channel.
Modern recordings are seldom made in this format, but older movies and music are available only in this format.
You may get mono from any source - digital or analog. Sound will normally come from the seven speaker
channels, but your processor can produce mono in one to seven channels (see “Audio Modes under Operation”).
Since all modern sources are stereo, the mono information is usually replicated from both the left and right
channels.