Compact Disc player
From Wikipedia, the free encyclopedia
A Compact Disc player (often written as compact disc player), or CD player, is an electronic device which plays audio Compact Discs. CD players are often installed into home stereo systems, car audio systems, and personal computers. They are also manufactured as portable devices. Modern units support other formats in addition to CDs; such as DVDs, CD-ROMs with audio files and video CDs. DJs often use players with adjustable playback sampling rate to alter the pitch of the music programme. Many modern CD players also include the capability to play MP3 CD's. CD playback functionality is also available on all modern CD-ROM/DVD-ROM drive equipped computers as well as on DVD players and CD-ROM/DVD-ROM based game consoles.
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[edit] Physical description
Most home CD players are contained in a plastic casing, which also houses the electrical system and the user interface. CD players designed for car audio systems or computers generally have a front casing and exposed sides and back, as these parts will be covered by the car or computer.
The housing of a portable CD player also contains ports used to connect the player to a powered or unpowered speaker, headphones and/or a power system (see electrical wiring in the United States or in the UK). A portable CD player generally contains an internal power source in the form of batteries.
The housing of a stand-alone CD player contains speakers and perhaps a radio and/or tape deck. CD players used in component audio systems contain a power source, the user interface, and numerous ports to connect the player to the various parts of an audio system.
[edit] Tray Design Evolution
[edit] Tray Loading
Sony released the world's first CD Player called the CDP-101[1] in 1982 utilising a slide-out tray design for the CD. As it was easy to use and manufacture, most CD player tray designs had followed this style of tray ever since. However there have been some notable exceptions.
[edit] Vertical Loading
During the launch of the first prototype CD player 'Goronta'[2] by Sony at the Japanese Audio Fair in 1981, Sony showcased the vertical loading design of the CD player. Although the prototype's design was never really put into actual production, it was for a time adopted for production by a number of early Japanese CD player manufacturers including Alpine/Luxman, Matsushita under the Technics brand, Kenwood and Toshiba/Aurex. For the early vertical loading players, Alpine sourced their AD-7100 player designs for Luxman[3], Kenwood and Toshiba (using their Aurex brand). Kenwood added their 'Sigma Drive' outputs to this design as a modification. A picture of this early design can be seen on the Panasonic website.[4]
[edit] Top Loading
In 1983 at the launch of the CD format, Philips with their FD-1000 CD player[5] (sold as Magnavox in the US), showcased the first top loading CD tray designs. The design had a clamp on the lid which meant the user had to close this over the CD when it was placed inside the machine. Apart from having no motors accessing a movable tray, thus interfering with the player's sound quality, as the disc was clamped right down within the player, it implied better sound quality. This was one of the primary reasons manufacturer Meridian created their MCD CD player,[6] whose chassis design was derived from Philips FD-1000.
Apart from being adopted on various stereo equipment designs such as mini components, over the years only a handful of hi-fi quality top loading tray CD players had been made. The most notable were Luxman's D-500 and D-500X series[7] players, and Denon's DP-S1,[8] both launched in 1993.
[edit] Tray Load with Sliding Mechanism
Meridians 200 and 203 players were the first players to adopt tray loading with sliding play mechanism. Basically as the tray came out to collect the CD, the entire player's transport system also came out as one unit. The players were also the first to utilise the CD Transport design whereby the audio electronics were separate from the CD drive mechanism itself to reduce jitter and distortion.
[edit] Tray Load with Dampers
A few companies produced CD players with dampened trays. The dampers were rubber grommets built into the tray to reduce distortion. Yamaha's CDX-1000 CD player was a good example of this design.
[edit] Function
A CD player has three major components: a drive motor, a lens system, and a tracking mechanism. The drive motor rotates the disc between 200 and 500 revolutions per minute. The tracking mechanism moves the lens system along the spiral tracks in which information is encoded, and the lens reads the information using a laser beam. The laser reads information by focusing a beam on the CD, which is reflected back to sensor. The sensor detects changes in the beam, and interprets these changes to read the data. This data is output as sound using a digital-to-analog converter (DAC).
A subcode in an audio CD contains information on the total number of audio tracks, the running time on the CD, running time of each track, and other information. This information allows the drive motor to speed up or slow down as needed to read data at a constant rate.
[edit] Interface
The interface of a CD player does not vary widely from manufacturer to manufacturer. It is usually comprised of a few buttons and a display device. Common buttons include play, pause, stop, advance/fast forward, back/rewind and, in the case of a multiple-CD player, disk selection. The display may provide information such as track number, track time, disk number in the case of multiple-CD changers and CD-Text.
[edit] CD changer
A CD changer holds multiple Compact Discs, usually in a cartridge, and allows the user to access (or play) any of them, one at a time. CD changers are commonly found in home cinema systems, cars, and less often in computer equipment.
[edit] Prior art
Prior to real CD changers being introduced, an attempt was made to copy the double cassette players found in many audio systems. As a result, devices with two separate, fully functional CD players were made. Double-cassette decks were never replaced with a cassette changer, mainly because a double-cassette deck could copy from one cassette to another. Double-CD decks, on the other hand, did not have this copy functionality since recordable CDs were not commercially available. Therefore, the shift to changers was swift, removing the need for double CD players.
[edit] Main types of CD changers
[edit] External cartridge
External cartridge CD changers have one or more cartridges that the user loads with up to 10 different CDs and then inserts into the CD changer. The CD changer can then remove one CD at a time for playing. This type of player is commonly found in vehicles because the user can switch easily between large amounts of media contained in different cartridges.
[edit] Internal cartridge
Internal cartridge CD changers work on the same basic principle as external cartridge players, except the cartridge never leaves the CD player. This type of CD player accepts multiple CDs through a single slot and stores them internally.
[edit] Carousel
A carousel type CD changer consists of a circular platter that holds three or more CD's. Traditional carousel CD players hold three, five, or seven discs on a flat carousel tray. The carousel ejects to allow access to the CDs. Once back inside, the CD changer can rotate the carousel to access all of the CDs. Such carousel CD changers often allow the user to rotate the carousel while open, and change all CDs if no CDs are currently playing, or to eject the carousel while one CD is playing to change any CDs accessible from that position. Another type of carousel CD players is the mega-disc or jukebox CD players as they are also known as. The hold anywhere from 50 to 300 discs. The mega-disc CD player holds it's discs in a vertical position in slots that located 360 degrees around the carousel. When a disc is selected to be played, the carousel rotates so that the disc can be picked up by a pickup mechanism and placed in CD playback unit. Mega-disc CD players generally have a means of entering in titles of the CD's stored inside them, such as telephone style letter input system found on the remote control, a full letter keypad on the unit, or by use of an external keyboard attached to the unit. Many units can also automatically obtain the title of a CD's if it contains CD-Text info stored on it.
[edit] Evolution
Digital audio players have surpassed the concept of CD changers. For example, the first generation iPod can hold an equivalent of 50 discs (1000 songs)[9] with a 128k bit rate for each song; thereby, the iPod is 1/10 the size of a CD changer cartridge, and about 1/20 the size of a carousel changer. Solid state flash-based digital audio players have rendered compact discs and thus CD changers obsolete for some purposes. While digital audio players often use a lossy compression scheme, they usually can accept lossless formats such as WAV (PCM) as well, matching the quality of CD audio.
[edit] Computer-based changers
As file format size shrinks, the same capacity discs may be sufficient for growing needs of storage. However, the amount of storage space needed may be growing faster than current compression abilities can handle. As a result, newer disc formats have been created, such as DVD-ROM/DVD+/-R, DVD-RAM, Blu-Ray, HD DVD, and holographic discs.
As consumer needs extend to the point where the cost of individual drives are prohibitive, CD changers can again become useful. Unfortunately, most disc changers are still intended primarily for large enterprises with unlimited budgets.
[edit] See also
- Compact Disc
- Hi-Fi
- High-end audio
- Jukebox
- MP3 CD
- Radio cassette
- Radio receiver, includes information about Radio CD.
- Record changer
- Transport (recording)
[edit] Notes
- ^ CDP-101 The first Compact Disc Audio CD Player from 1982 (2007). Retrieved on February 5, 2007.
- ^ Sony History (2007). Retrieved on February 5, 2007.
- ^ Luxman DX-104 CD Player (2007). Retrieved on February 17, 2007.
- ^ Panasonic History - Innovative Products - 1982 - CD Player (2007). Retrieved on February 5, 2007.
- ^ Audion Circuit Review - Magnavox FD1000 Compact Disc Player (2007). Retrieved on February 5, 2007.
- ^ Meridian CD History (2007). Retrieved on February 5, 2007.
- ^ Luxman D-500X (in Japanese) (2007). Retrieved on February 5, 2007.
- ^ Denon Museum - Model History - 1993 - DP-S1 (in Japanese) (2007). Retrieved on February 5, 2007.
- ^ http://www.apple.com/pr/library/2001/oct/23ipod.html
