High Definition Compatible Digital (HDCD)
High Definition Compatible Digital (HDCD) is one of several recent improvements in the coding of the familiar compact disc. HDCD discs, developed by Pacific Microsomes, are created using a faster sampling rate of 96 kHz, as compared to the conventional 44.1 kHz used on present CDs, and with 20-bit data units. If this were coded directly on to the CD it would not be compatible with existing CDs, so data are compressed to 16-bit units and a 44.1-kHz pulse rate.
The result is that the HDCD discs can be played on a normal CD deck, but these discs will deliver more dynamic range and overall better sound on a player that uses HDCD decoding. Discs prepared in this way can be recognized by the use of a distinctive HDCD logo.
The first firms to offer players with HDCD capability were Denon, Harman Kardon, Rotel, and Toshiba. Although more than 4000 titles are available in the United States at the time of this writing, these and HDCD players are not easy to find in the United Kingdom (one of the recent offerings is from the respected firm of Linn). The players contain interpolation circuitry that can also enhance conventional CDs, and HDCD has, as you would expect, arrived mainly on the players in the £1000 upwards price bracket. Players indicate the presence of an HDCD disc by lighting an indicator. Note that the most recent Philips CD recorder caters to copying HDCD discs.