SACD

(Super Audio CD) A high-resolution CD audio format from Sony and Philips. SACD and DVD-Audio (DVD-A) were the two next-generation digital audio formats for enhanced sound quality, but neither one caught on (see high-resolution audio).

SACD uses Direct Stream Digital (DSD) technology which provides 1-bit pulse density modulation (PDM) encoding at 2,822,400 samples per second. Each sample is a 0 or 1 (up or down), depending on its relationship to the previous sample. Compared to CD, SACD boosts frequency response from 20 kHz to 100 kHz and dynamic range from 96 to 120 db. See PDM.

Multi-Channel Support
Introduced with only two channels for stereo, 5.1 multi-channel support was later added. In 1999, Sony's SCD-1 was the first SACD player on the market. Its $5,000 price placed it squarely in the audiophile league, but subsequent players moved SACD well into the consumer realm, with combo units that also play DVD-Audio, DVDs and CDs for less than $200.

Hybrid SACDs
Introduced in 2003, hybrid SACD discs include a separate CD layer with the same titles so they can play in regular CD players. See DVD-Audio.

The DSD Approach

Sony's SACD audio format is a dramatic departure from PCM, the common way audio is sampled. Direct Stream Digital (DSD) 1-bit samples are either 0 or 1 (up or down) depending on the previous sample point.

SACD and More

The Compli is a very high-end audio deck from Theta Digital that plays every type of audio and video format, including audio CD, MP3, SACD, DVD-Audio, Video CD and DVD. (Image courtesy of Theta Digital, www.thetadigital.com)