612 Chapter 21
21.2 High Defi nition Compatible Digital (HDCD) .......................................................
High Defi nition Compatible Digital (HDCD) is one of several recent improvements in the
coding of the familiar compact disc. HDCD discs, developed by Pacifi c 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 fi rst fi rms 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 fi nd in the United
Kingdom (one of the recent offerings is from the respected fi rm 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.
21.3 CD Writers ............................................................................................................
CD writer drives have become commonplace on PC computers where they are used
primarily for making backup copies of valuable data and programs, but they are still a
fairly rare sight on hi-fi installations. The CD writer drives as used in computers have
several advantages:
- They are considerably less expensive.
- They allow you to store computer data, including still or moving images, as well
as sound. - They are compact, fi tting into a 5¼-inch drive space.
- You can decide for yourself what software to use with them.
- They can use either write-once (CD-R) or read-rewrite (CD-RW) discs.
- They can make recordings at a higher speed than music can be played.