It's important to know that "Quad" DSD does not refer to a four channel surround playback system. When Quad is used with DSD it refers to a stereo download that is four times bigger than the DSD 64 files. The term came into use after "Double DSD" files became available. Another name for quad DSD is DSD256 or DSD 11.2 Megahertz (or 11.2MHz). These files are very large (8-10 gigabytes for a typical album) and require special playback systems. Before purchasing, make sure your devices can play 'Quad' DSD.