Connections & formats

DSD

Also called Direct Stream Digital, DSD64, DSD256, SACD

DSD, Direct Stream Digital, stores audio as a one-bit stream at a very high rate, 2.8 MHz for the DSD64 used on SACD, rather than as multi-bit PCM samples. It is a niche format for downloads and SACD discs, supported by many DACs.

DSD stores one bit per sample at a very high rate, about 2.8 million samples per second for DSD64, 64 times the CD rate. Where the waveform is high the stream is mostly 1s, and where it is low mostly 0s (simplified).

DSD is the raw output of a delta-sigma modulator saved to disc. Sony and Philips introduced it with the Super Audio CD in 1999, and labels such as Channel Classics still record in it. Higher rates, DSD128 and DSD256, push the noise-shaped high-frequency noise further out of the audio band.

Because it cannot be edited or mixed without converting to PCM, many "DSD" releases were PCM at some stage. Playing it needs a DAC that accepts DSD over USB, usually packed as DoP, since optical and coaxial links rarely carry it. Fans describe a smooth, analog-like sound; blind tests have not shown it to beat hi-res PCM of the same master, and listeners disagree.

Related terms