High Definition Audio Formats for Music Listening - SACD (1) 
The Super Audio CD - An Introduction

The Super Audio CD - or SACD for short, is one of the new high definition multi-channel audio formats designed specifically for music listening. In the first part of this article, we discuss the Super Audio compact disc, audio specifications, format variations and the Hybrid disc.

The Super Audio CD: An Introduction

The Super Audio Compact Disc was originally developed by Sony and Philips Electronics in 1999, the same companies that created the CD.

It is a read-only optical audio disc designed to provide a much higher audio quality than that supported by the CD-Digital Audio format.

The SACD audio disc supports high-resolution sound in either two-channel stereo or multi-channel audio, with up to six full-range discrete channels of music. In addition, it also supports storage capacity for text, images, copyright protection, and more. Basically, this is the same as its DVD-Audio counterpart. However, unlike DVD-A, the Super Audio CD does not use PCM. Instead, it is based on what is called Digital Stream Direct (DSD); this is fundamentally different from PCM.

Thanks to this DSD encoding technology, SACD audio is capable of delivering improved frequency response and extended dynamic range, leading to a more analog-like performance in terms of music reproduction, than that possible with CD Audio.

Yet, like its DVD-Audio competitor, the Super Audio CD has still a long way to go to acquire the desired level of consumer acceptance. Figures released by the Recording Industry Association of America (RIAA) for the first six months of 2006, show that both SACD and DVD-Audio had 0.1 million units each to retail; these figures contrasts heavily with the 221 million CDs and 9.2 million DVD-videos. Worst still is the fact that these new high resolution audio formats have come at a time when all forms of physical media content - whether it is music or video, are experiencing a negative trend in sales as against the present explosive growth in digital downloads.

To make things worst, the format war between SACD and DVD-Audio, especially during the first years of their existence, left many end-customers somewhat uncomfortable to jump onto the bandwagon of high-resolution audio. 

Today, things are changing fast. The availability of inexpensive universal DVD players like the OPPO DV-970HD up-converting universal player, or the Onkyo DVSP504 universal DVD player (pictured on the right), has rendered this format war a non-issue.

In addition, the fact that Super Audio CDs and DVD-Audio discs are being priced at CD levels is leading to a situation among music lovers and audiophiles alike, where choice is driven solely by music content rather then audio format.

Further more, the present shift towards hybrid discs - featuring a CD layer for backward compatibility with standard CD players, is surely making it much easier for end-customers to shift their choice towards these high-resolution audio discs.

This means that even if most customers do not yet possess the necessary audio playback setup to get the very best out of these high-definition audio formats, yet they have the possibility to start building their high resolution audio disc collection, while enjoying standard CD audio till the time comes to upgrade their gear.

The SACD - Disc Specifications

The Super Audio CD disc itself looks like an ordinary audio CD or DVD disc.  Yet the basic SACD disc is closer to a DVD in terms of physical characteristics and data capacity. The table below compares the SACD disc with an audio CD.

There are three types of Super Audio CD Discs:

• Single-layer SACD: Physically, this is a DVD-5 DVD with a 4.7GB high density layer only for stereo and/or multi-channel DSD recording - capable of delivering up to 100 minutes of high resolution stereo or 80 minutes of multi-channel + stereo sound.

• Dual-layer SACD: Physically, a DVD-9 DVD with two high-density layers for a total of 8.54GB capacity - thus enabling longer playing times of either 2-channel or multi-channel DSD recording.

• Hybrid SACD: This is the most popular of the three. The hybrid disc is somewhat similar to the dual-layer disc in terms of concept, in that it contains a high-density SACD layer and an audio CD layer physically bonded on the same disc. This makes the disc looks like a regular audio CD disc to a CD player or CD-ROM drive.

The Hybrid SACD and Backward Compatibility

While the single or dual layer Super Audio CD discs are not backward compatible with CD players, yet the presence of a CD-layer in a Hybrid SACD disc renders the latter playable on any of the hundreds of millions of CD playback equipment worldwide.

The Hybrid SACD process is possible because the high density layer - while acting as a reflective surface to the shorter wavelength SACD laser, is penetrated by the 780nm laser rays used by CD-DA. Further more, the objective lenses used by the CD-DA and SACD lasers focus the laser rays at different distances (1.2mm and 0.6mm respectively), in accordance with the different layer depths. (Ref. to diagram).

Thus, when the hybrid disc is placed in an SACD player, the laser is reflected by the high-resolution layer (at 600 µm distance) before it can reach the conventional layer. Similarly, if a conventional CD is placed into an SACD player, the laser will read the disc without difficulty since there is no high-resolution layer.

Hybrid discs are always marked as either 'Hybrid SACD' or as 'compatible with all CD players'.

Note: The CD layer on a Hybrid SACD would only reproduce CD-quality stereo sound. To enjoy high resolution stereo or the multi-channel sound present on the DSD soundtrack, you need a Super Audio CD compatible player; the latter is also capable of playing regular audio CDs.

Format Variations

As already indicated, SACD discs may come in stereo and/or multi-channel audio. In all, there are four main variations of the Super Audio CD.

Stereo Variants:
	Discs with this emblem will only play in Super Audio CD players.
	These discs play in all standard CD players, as well as Super Audio CD players.
Multi-Channel Variants: Multi-channel can include anything from 3 to 5.1 channels of audio. Each multi-channel disc also includes a separate two-channel version of the music for complete compatibility with two-channel Super Audio CD players.
	These discs will only play in Super Audio CD players, providing stereo sound on two-channel players and multi-channel sound on multi-channel players.
	Discs with this graphic will play stereo sound in all CD players, as well as stereo and/or multi-channel high resolution sound in compatible Super Audio CD players.

More on the Super Audio CD will follow soon.	Last updated on: 4th March 2007
Subscribe to our free e-zine to remain abreast with the latest additions. Click here for details.

 

  ...Part 2:DSD - The Technology behind SACD

...back to DVD-A/SACD Section Index

 Copyright © - Practical-Home-Theater-Guide.com  All rights reserved.