Then There Was DVD
In 1995, DVD came along. DVD stands for Digital Versatile Disk, and can store approximately six times as much data as a CD. It was used first to store video. DVD players were backwards compatible which meant that they could play CDs as well. However, these disks could be used for other things too. As well as DVD-Video, a DVD-audio disk was introduced, using the higher capacity to store more channels (up to 5.1) and at higher resolutions. These disks had another layer encoded into them, which used the compressed Dolby Digital or DTS systems to replay multi-channel sound at the same resolution as DVD-Video. This meant that all DVD players could use these disks, but only DVD-Audio players would replay at the highest quality.
Meanwhile, Philips and Sony produced a different high quality audio system known as SACD. SACD players could replay the high quality SACD disks and CDs, but not DVDs. To really confuse matters, most SACD disks, but not all, included a CD layer which could replay on all CD players.
By now consumers were becoming frustrated and confused (are you surprised?) and started to demand players that could play all of the formats. Two solutions emerged.
Universal audio disk players could replay all the disks in their native formats and DVD videos as well. Examples such as the Pioneer 656 and then the 565 universal players provided these facilities at remarkably low prices. These were followed by machines like the Denon 1940 which included upscaling of DVD-video signals for replay on flat screen televisions.
However, there was also a group of what I shall call almost universal players, that played all the disks including SACD in native format, but did not reproduce the high quality DVD audio signals, replaying instead the lower quality compressed layer.