Super Audio Cd; Overview; The New Format For The Age Of Digital Pure Audio - Sony STR-DE845 Training Manual

13. Super Audio Cd

Super Audio CD

Overview

Developed by Sony and Philips in early 1982, the compact disc (CD) was a revolutionary development that
overturned conventional thinking about audio media. Unlike the analogue recordings, which were mainstream at
that time, the CD system converted music signals into digital signals for recording and playback. Users were
amazed by the dramatic improvement in sound quality, the quick access and the handling convenience provided
by the compact 12cm discs. With so many merits, the CD quickly penetrated the market and has become one of
the most commonly used audio formats of our time.
The CD uses a PCM (Pulse Code Modulation) recording format, in which music signals are converted into digital
data for each sampling frequency and represented at each stage as a quantization bit number. When the PCM
format was being developed, engineers aimed to achieve a 44.1kHz sampling frequency and a 16-bit quantization
for recording and playback of digital data. This goal, which they hoped to establish as the standard for the CD
format, represented a level that greatly exceeded the technology available at that time. Eventually, progress in
A/D converters and other equipment on the recording side, as well as technical developments for digital filters
and D/A converters on the playback side, enabled engineers to achieve this goal.
At the time the CD format was being developed, PCM represented the most advanced technology available in
the recording field, and rightly so, the music industry welcomed it gladly as a playback standard. However,
although the playback frequency range and dynamic range were designed to match the audible range of human
hearing, they represented just one small portion of the sounds that exist in nature. With the continuous progress
being made in digital technology, it became possible to make recordings that contained a greater volume of
information, allowing for further improvements in sound quality. These technical developments opened the door
for the creation of a new source media format with even higher sound quality, surpassing the limits of the CD. As
expected, the music industry welcomed these new possibilities as a means to assuring the quality and longevity
of their new masters and for preserving their valuable archives from deterioration over time.
In response to these technical developments, Sony and Philips once again joined forces, resulting in the creating
of the Super Audio CD. The Super Audio CD is expected to become the new source media for the next century.
Rather than simply offering improvements in the sampling frequency or level of quantization, Super Audio CD
represents a revolution in the way digital data is recorded and played back. With Super Audio CD, sound signals
are converted using Direct Stream Digital (DSD) technology, a completely new approach to digital recording.

The New Format for the Age of Digital Pure Audio

Simply put, the DSD format expresses music signals according to the concentration of their pulse waves, as
shown in Figure 13-1. The shape of the wave is the same as that of a wave of compression and rarefaction that
travels through the air. Although the sound signals expressed by DSD are digital data, they contain properties
that are extremely similar to the actual sound wave. In principle, by passing these signals through an analogue
low-pass filter, it is possible to retrieve the original analogue signals in the playback stage.
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