Direct Stream Digi
Direct-Stream Digital (DSD) is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media that are used for the Super Audio CD (SACD).
The signal is stored as delta-sigma modulated digital audio, a sequence of single bit values at a sampling rate of 64 times the CD Audio sampling rates of 44.1 kHz, for a rate of 2.8224 MHz (1 bit times 64 times 44.1 kHz). Noise shaping occurs by use of the 64× oversampled signal to reduce noise/distortion caused by the inaccuracy of quantization of the audio signal to a single bit. Therefore it is a topic of discussion whether it is possible to eliminate distortion in 1-bit Sigma-Delta conversion.
Practical DSD converter implementations were pioneered by Andreas Koch and Ed Meitner, the original founders of EMM Labs. Andreas Koch later left EMM Labs and along with Jonathan Tinn, founded Playback Designs who have pioneered the transfer of DSD files over USB connections. Global DSD technology was developed by Sony and Philips, the designers of the audio CD. Philips' DSD tool division was transferred to Sonic Studio, LLC in 2005 for on-going design and development.