Super Audio CD

Sony and Philips, the inventors of CD have invented SACD to replace it
It uses a technology called Direct Stream Digital (DSD) encoding.
The frequency response delivered by DSD is almost five times greater than that delivered by normal CD. And with a dynamic range of 120dB compared to 96dB on CD the differences are clear to hear.
Discs can be multichannel encoded with up to 5.1 channels of information or just normal stereo and some (hybrid) discs are compatible with exciting CD players by using two layers (One for the SACD and one for normal CD)
Most SACD discs are only compatible with SACD players
SACD is a rival format to DVD-Audio although many players can now play formats both eliminating the worry over which format will replace CD.