Cassette deck
From Wikipedia, the free encyclopedia
A cassette deck is a type of tape recorder for playing or recording compact audio cassettes. A deck was formerly distinguished from a recorder by containing no amplifier or speakers for direct listening, except a headphone jack. The deck is connected to a sound system for playback. The two terms are often now used interchangably.
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[edit] History
[edit] Origins
The cassette recorder was introduced by the Philips Corporation in 1963 and marketed in 1965 as a device for vocal dictation designed for portable use. It was not intended to be a replacement for reel-to-reel recorders. It enclosed both reels of the recording tape in a small case which eliminated the need to thread the tape through individual reels. The tape width was just 0.125 inches (3.2 mm) and tape speed was 1.875 inches (4.76 cm) per second, which meant that sound quality was appropriate only for voice or dictation use at the time with high end response dropping off beyond 10 KHz and high noise levels.
Early recorders tended to be small battery-powered portable devices with automatic level control, in keeping with the intention of the medium for dictation, reportage and similar low-level recording duties, but by the mid 1970s, the cassette deck with manual level controls and VU meters became a commonplace component of home high fidelity systems. Eventually they replaced the reel-to-reel recorder, which had found only limited home use because of their large size and inconvenience of threading and rewinding the tape reels. A cassette can be removed in the middle of the tape without rewinding. Cassettes can also be used in automobile and personal portable applications. The common practice of splicing (cutting pieces of tape and attaching them together with adhesive tape) songs together was impractical for cassette, as users typically simply recorded songs off records in sequence to make a "road tape". Cutting blocks and related materials were available for cassettes and used for repairing damaged tapes.
In 1971, the Advent Corporation combined Dolby B-type tape-hiss-noise reduction system with chromium dioxide tape to create the Advent Model 201, the first high-fidelity cassette deck. Dolby B raises treble levels well above the noise level, and reduces them on playback, while CrO2 used different bias and equalization settings to do much the same, and extended frequency response into high fidelity range beyond 15 KHz for the first time. This deck was based on a top loading mechanism by Wollensak, a division of 3M which was commonly used in audio / visual applications. It featured an unusual single VU meter which could be switched between or for both channels, and lever operated controls, similar to those used on reel-to-reel mechanisms.
Most other manufacturers adopted a standard top loading format with piano key controls, dual VU meters, and slider level controls. There was a variety of configuations leading to the next standard format in the late 1970s, which settled on front-loading (see main picture) with cassette well on one side, dual VU meters on the other, and later a dual-cassette format with meters in the middle. Mechanical controls were first replaced with mechanically assisted and later full electronic buttons, though low cost models would retain mechanical controls. Some models could search and count gaps between songs. Cassette players pioneered the modern set of control buttons, play, pause, stop, record, fast forward and rewind. Unlike modern CD controls, most had a "locking" fast forward and rewind which could be depressed once, and remain until stopped. Most DVD players today lack even a fast forward or rewind control on the front panel to save on cost.
[edit] Widespread use
Cassette decks soon came into widespread use and were designed variously for professional applications, home audio systems, and for mobile use in cars, as well as portable recorders. From the mid 1970s to the late 1990s the cassette deck was the preferred music source for the automobile. Like an 8-track cartridge, it was relatively insensitive to vehicle motion, but it had superior frequency response and reduced tape flutter, as well as the obvious advantages of smaller physical size and fast forward/rewind capability.
[edit] Performance improvements
Cassette decks reached their pinnacle of performance and complexity by the mid 1980s. Cassette decks from companies such as Nakamichi, Revox, and Tandberg incorporated advanced features such as multiple tape heads and dual capstan drive without motorized reel motors. Auto-reversing decks came into popular use so the user did not need to flip the cassette manually to play the second side of the tape, and this was standard on all factory installed automobile decks, though this usually involved some ingenuity and compromise in head adjustments which changed slightly for each direction, and sometimes required a smaller set of erase and record and sometimes even 3rd monitor heads which had to fit into the middle opening and rotated. A cassette is nominally designed so that the first opening is for the erase head and the second is for the record / play head, though the third space could be used for a monitor head. Nakamichi got around this on one unit by physically rotating the entire cassette, leaving the transport and heads stationary.
Compact Decks sold by Japanese companies such as Akai, Pioneer, Sony, Technics, Yamaha, and Denon were also common, with each company offering models of very high quality. The best units could record and play the full audible spectrum from 20 Hz to 20 KHz with wow and flutter less than 0.05% and very low noise.
A very good live cassette recording could very well rival an average or poorly recorded commercial CD, though the quality of pre-recorded cassettes was usually considered less than home recording made with a high fidelity system. It was a common practice to only play a record once onto cassette, which could then be played over and over in various cassette players in the car or while walking. Cassettes remain popular for audio-visual applications as even some CD recorders include a cassette drive for providing both formats for recording meetings, church sermons and books on tape.
Three-head technology use separate heads for recording and playback. This enables hearing the actual recording as recorded on the tape. This was common on reel-to-reel decks which have no fixed head positions. But it is difficult for cassettes which do not provide an opening for separate reading and recording heads, especially so for reversing decks. These were developed first by Nakamichi, which specialized in high end decks, but was also adapted by other manufacturers.
Dolby noise reduction system was a key technology as slow, narrow tapes were prone to higher noise levels than reel-based players. It works by boosting high frequencies on recording and then restoring them, also lowering the constant high frequency noises. Enhanced versions including the newer C (in 1980) and S types, though the B system is the only standard supported on most high fidelity automobile decks. Some decks incorporated microprocessor programs to adjust tape bias automatically. Bang & Olufsen developed the HX-Pro headroom extension system in conjunction with Dolby Laboratories in 1982. This was used in many higher-end decks. Chromium dioxide was the first formulation for high fidelity, but it required a special bias and equalization and switch (II), later decks incorporated coded holes in the shell to detect this. TDK and Maxell adapted ferric formulations to mimic CrO2 which urban legend held would quickly wear out heads. Sony briefly tried FerriChrome which combined the best of both (III). Most decks today produce the best response with metal oxide tapes which require yet another setting (IV), though they will play back at the II setting.
[edit] Noise reduction and fidelity
A variety of noise reduction and other schemes are used to increase fidelity, Dolby B being almost universal for both prerecorded tapes and home recording. Philips developed an alternative noise reduction system known as Dynamic Noise Limiter (DNL) which did not require the tapes to be processed during recording.[1] Other alternatives included the dbx and DNR noise reduction systems. Later enhancements to Dolby included Dolby C and Dolby S noise reduction, Dolby HX Pro headroom extension, Toshiba's ADRES and Telefunken's Hi-Com, and on some high-end decks, automatic recording bias and head azimuth adjustment. Dolby HX Pro, which was developed by Bang & Olufsen, is a system that dynamically alters the recording bias to yield a substantial improvement in high-frequency response during playback, regardless of the playback system.
By the late 1980s, thanks to such improvements in the electronics, the tape material and manufacturing techniques, as well as dramatic improvements to the precision of the cassette shell, tape heads and transport mechanics, sound fidelity on equipment from the top manufacturers far surpassed the levels originally expected of the medium. On suitable audio equipment, cassettes could produce a very pleasant listening experience. The best home decks could achieve 20 Hz-20 kHz frequency response with wow and flutter below 0.05%, and 70 dB of signal-to-noise ratio using Dolby C and up to 80 dB of signal-to-noise ratio using Dolby S. On decks with Dolby S, listening tests showed that most people could not tell the difference between cassette and compact disc.[citation needed]
Average equipement achieves 30 Hz-15 kHz frequency response with wow and flutter below 0.1%, and least 55dB of signal-to-noise ratio using no Dolby noise reduction, 63dB of signal-to-noise ratio using Dolby B and 70dB of signal-to-noise ratio using Dolby C. Usage of Type II tapes improves signal-to-noise ratio by 2dB and Type IV gives an extra 1dB.
In the 1990's, Dolby S noise reduction was introduced to the compact cassette, derived from Dolby SR, a professional system. Whereas the Dolby B and C Noise Reduction would dynamically adjust the preemphasis to promote a lower noise floor for high frequencies, Dolby S worked across the frequency range. However, licensing restrictions meant that Dolby S was only available on higher end tape decks that included dual motors, triple heads and other refinements. This system, according to a double blind study conducted by Stereo Review, yielded more accurate results than MiniDisc.
Prior to the mid 1980's pre-recorded cassettes were often of poor sound quality mainly due to the high speed duplication process used to produce them. However, technologies such as XDR (a quality control system), Dolby B Noise Reduction, Dolby HX pro and chrome dioxide tape meant that pre-recorded cassettes were soon approaching vinyl records in terms of audio quality and outselling LP records in some markets.
[edit] In-car entertainment systems
Another key element of the cassette's success was its use in in-car entertainment systems, where the small size of the tape was significantly more convenient than the competing 8-track cartridge system. Cassette players in cars and for home use were often integrated with a radio receiver, and the term "casseiver" was occasionally used for combination units for home use. In-car cassette players were the first to adopt the idea of automatic reversal ("auto-reverse") of the tape at each end, allowing a cassette to be played endlessly without manual intervention. Home cassette decks soon followed this practice as well.
Later on Cassette tape adaptors were developed, allowing newer forms of music player to be used with existing cassette-based systems, including those in cars. (See "Successors to the cassette" below).
Companies such as Tandberg, ReVox, Nakamichi, Akai, Aiwa, Technics, Pioneer and Sony made highly advanced cassette decks for high-end audio systems. Some include three-head technology for off-tape monitoring.
[edit] Maintenance
Cassette equipment needs regular maintenance, as cassette tape is a magnetic medium which is in physical contact with the tape head and other metallic parts of the recorder/player mechanism. Without such maintenance, the high frequency response of the cassette equipment will suffer.
One problem occurs when iron oxide (or similar) particles from the tape itself become lodged in the read head. As a result, the tape heads will require occasional cleaning to remove such particles. The metal capstan and the rubber pinch roller can become coated with these particles, leading them to pull the tape less precisely over the head; this in turn leads to misalignment of the tape over the head azimuth, producing noticeably unclear high tones, just as if the head itself were out of alignment.
In addition, the heads and other metallic components in the tape path (such as spindles and capstans) may become magnetised, and require demagnetization. Both Cassette demagnetizers and head-cleaning fluid are available. Isopropyl alcohol is commonly used as a tape head cleaner.
[edit] Decline in popularity
Analog cassette deck sales began to decline with the advent of the compact disc and other digital recording technologies such as digital audio tape (DAT). Philips responded with the digital compact cassette, but it failed to garner a significant market share and was withdrawn. Tascam, Marantz, Yamaha, Teac, Denon, Sony, and JVC are among the companies still manufacturing cassette decks in relatively small quantities for professional and niche market use.
Despite the decline in the production of cassette decks, these products are still valued by some. Some audiophiles believe that cassette deck technology, due to its analog nature, provides sound recordings superior to current digital technology, such as CDR and DAT. However, cassette decks are not considered by most people today to be either the most versatile or highest fidelity sound recording devices available.
[edit] See also
- Tape deck
- Nakamichi and Revox. These corporate pages contains links to external sites relevant to cassette decks.
- high end audio. This page contains links to high-end audio companies, including companies formerly producing "high-end" audio gear such as cassette decks.
[edit] Notes
- ^ Circuit and description of DNL URL accessed August 25, 2006
[edit] External links
- Pictures of Cassette Decks – A Japanese language page, but containing pictures of historic cassette decks.
- Vintage Deck Pictures – An external link with pictures of vintage cassette decks and reel to reel decks.
- Audio Asylum Tape Trail – A discussion forum of interest to those involved in cassette technology.
- Vintage Cassette Decks - A collection of Vintage cassette decks of all brands.
