Direct Stream Digital (DSD) is a trademark used by Sony and Philips for their system for digitally encoding audio signals for the Super Audio CD (SACD).
DSD uses delta-sigma modulation a form of pulse-density modulation encoding, a technique to represent audio signals in digital format, a sequence of single-bit values at a sampling rate of 2.8224 MHz. This is 64 times the CD audio sampling rate of 44.1 kHz, but with 1-bit samples instead of 16-bit samples. Noise shaping of the 64-times oversampled signal provides low quantization noise and low distortion in the audible bandwidth necessary for high resolution audio.
DSD is simply a format for storing a delta-sigma signal without applying a decimation process that converts the signal to a PCM signal.
Development
DSD technology was developed and commercialized by Sony and Philips, the designers of the audio CD. However, in 2005, Philips sold its DSD tool division to Sonic Studio.
Major label support
DVD-Audio was endorsed by the Warner Music Group, while the SACD format was endorsed by Sony and Universal Music Group, with an especially high-profile by UMG imprint Virgin Records. Despite this, in 2011, The Warner Premium Sound series of albums was released by Warner Music Group, marking the first time the label released titles in a SACD format, with recording in DSD. The series grew to ten rock and pop albums, with Super Audio CD/CD hybrid discs containing both an SACD layer and a standard CD layer.
Sony did not promote SACD actively in North America, with the result that DVD-Audio gained competitive traction in the market. Elsewhere, such as in Europe or Japan, SACD gained more of a foothold. Examples include the German Stockfisch Records, which releases vinyl editions of albums and DSD-recordings, released as hybrid SACDs.
Independent label use
Music companies that specialize in Super Audio CD products therefore use DSD encoding. A number of independent record labels have also worked directly with Sony to focus on DSD products or the DSD recording process.
DMP Digital Music Products was an early user of the SACD digital audio format. In 1997 their release Alto by Joe Beck & Ali Ryerson was the first commercial recording captured with Sony's DSD recording technology. The label's Just Jobim by Manfredo Fest in 1998 was the first project captured with the new Meitner DSD conversion technology. In 2000, DMP released the world's first multi-channel SACD—Sacred Feast by Gaudeamus.
The majority of Telarc International Corporation's releases were on (generally hybrid) SACD, and are DSD recordings. Telarc often worked with early audiophile company Soundstream, and re-released many of its original Soundstream recordings in SACD format. Soundstream, which made the first digital recording in the United States, recorded in 16-bit PCM at a sample rate of 50 kHz via its own proprietary digital recorder. This 50 kHz PCM format was converted to DSD for release on Telarc SACD.
The record label Mobile Fidelity had engineers who decided to adopt the SACD over the DVD-Audio disc as a favored high-resolution digital format after listening tests and technical evaluations. On the label's Hybrid SACD releases, the SACD layer is a direct DSD recording of the analog master tape, while the CD layer is a digital down conversion of the DSD, with Super Bit Mapping applied. Post-2001, CD-only releases are sourced from DSD, but omit the SACD layer.
In 2007, Blue Coast Records was founded in California for the purpose of recording and releasing music recorded with the DSD format, primarily focusing on jazz and acoustic artists.
On August 28, 2013, the Acoustic Sounds label launched SuperHiRez.com (now defunct), which sold mainstream albums from major record labels that were produced with Direct Stream Digital or PCM audio formats. On September 4, 2013, Acoustic Sounds announced an agreement with Sony Music Entertainment to provide the company's new digital download service with albums that have been produced or remastered in DSD format.
The format is used on albums such as Pop, Songs & Death in 2009, and the remastered The Rolling Stones album Their Satanic Majesties Request in 2002.
DSD signal format
DSD differs from the PCM format used by compact disc or typical computer audio systems: while PCM uses a multi-bit value (representing a large range of amplitudes) at a low sample rate, DSD instead uses a single-bit value (representing an increase or decrease in amplitude) at a sample rate much higher than the signal's bandwidth.