Super Audio CD

Overview

SACD is a disc of identical physical dimensions to a standard compact disc; the density of the disc is the same as a DVD and it encodes audio using a process known as Direct Stream Digital. The SACD sampling rate is 2822.4 kHz and the resolution is one bit. A stereo SACD recording can stream data at an uncompressed rate of 5.6 Mbps; four times the rate for Red Book CD stereo audio.^[1] SACD recordings can have a wider frequency and dynamic range than conventional CDs.

There are three types of SACDs:^[1]

• Hybrid: The most popular of the three types, hybrid discs include a Red Book layer compatible with most ordinary Compact Disc players, dubbed the "CD layer," and a 4.7 GB SACD layer, dubbed the "HD layer."^[2]
• Single-layer: Physically a DVD-5 DVD, a single-layer SACD includes a 4.7 GB HD layer with no CD layer.
• Dual-layer: Physically a DVD-9 DVD, a dual-layer SACD includes two HD layers totaling 8.5 GB, with no CD layer. It enables nearly twice as much data to be stored, but eliminates CD player compatibility. This type is rarely used.

Almost all commercially released SACDs have included both stereo and surround (multi-channel) mixes. A multi-channel mix need not be surround, however; some of the Living Stereo reissues (such as the RCA reissue of the 1957 Chicago Symphony Orchestra recording of Mussorgsky's Pictures at an Exhibition^[3]) use only the three front channels to reproduce the original three-track (3.0) stereo recordings. Nor is a surround mix obliged to use all six SACD channels (five full-range plus LFE). For example, the 2001 SACD release of Mike Oldfield's Tubular Bells remains in the quadraphonic 4.0 mix^[4]The CD layer exists primarily for backward compatibility, but is not required. If the CD layer is omitted, the SACD need not be limited to an 80-minute playing time. For stereo material, the space that would have been taken by the multi-channel program can be used to extend playing time to four hours or more. BIS has taken advantage of this to put all of Bach's organ music on five SACD-only disks.^[5]

Disc reading

How a hybrid Super Audio CD works

Objective lenses in conventional CD players have a longer working distance, or focal length, than lenses designed for SACD players. This means that when a hybrid SACD is placed into a conventional CD player, the laser beam passes the high-resolution layer and is reflected by the conventional layer at the standard 1.2 mm distance, and the high-density layer is out of focus. When the disc is placed into an SACD player, the laser is reflected by the high-resolution layer (at 600 µm distance) before it can reach the conventional layer. Conversely, if a conventional CD is placed into an SACD player, the laser will read the disc as a CD since there is no high-resolution layer.^[1][19]

[edit] Playback hardware

Hybrid Super Audio CDs (which include both CD and Super Audio CD layers) can be played on CD players. The SACD layer can be played only on a player that supports the SACD format. Not all SACD players support multi-channel playback—some are simply stereo.

The Sony SCD-1 was a player which was introduced concurrently with the SACD format in 1999, at a price of approximately US$5,000.^[24] It weighed over 26 kg (57 lb). The SCD-1, no longer produced, was introduced before multi-channel SACDs existed and played two channel SACDs and Red Book CDs only.

Many electronics manufacturers, including Denon,^[15] Marantz,^[25] Pioneer^[16] and Yamaha^[26] offer SACD players. None, however, has offered a portable SACD player capable of playing the high-definition layer of an SACD. Most portable CD players will play the conventional CD layer of a Hybrid SACD.

Sony has made in-car Super Audio CD players.^[27]

Several brands have introduced (mostly high-end) Blu-ray Disc players that are SACD-compatible.^[28]

SACD players are not permitted to offer an output carrying an unencrypted stream of Direct Stream Digital (DSD)^[29]. Players initially supported only analog output; later some proprietary digital interfaces such as Denon Link permitted encrypted transmission of DSD. There are now two standard digital connection methods capable of carrying DSD in encrypted form: i.Link and HDMI (version 1.2 or later, standardised in August 2005).

The older i.Link interface is generally found on older mid- to high-end equipment and some current top-of-the-line units from Japanese manufacturers. HDMI is more common, being the standard digital connection method for high-definition video with audio. Most new mid-level and higher 2007 model year and later A/V processors support the HDMI 1.2 specifications DSD over HDMI feature. Most boutique manufacturers still do not support DSD. Some HDMI 1.1 spec DVD players convert DSD to LPCM and then pass it to an HDMI 1.1 spec or later processor. Lower end processors usually convert the DSD to LPCM, higher end ones usually convert it to LPCM for bass management or DSP but can also process it natively at the expense of DSP and bass management. Some new DVD players from Oppo Digital, Pioneer, Onkyo, etc. now support HDMI 1.2 or 1.3 and will pass DSD over HDMI as well as LPCM. Be aware that some players, for instance, Onkyo DV-SP504, will not support DSD or LPCM over HDMI without resampling it to 48 kHz. SACD or DVD-A will be played through analog outputs instead. The older i.Link interface has been dropped from all but high-end A/V processors and DVD players.