Tagged: 4mm

Microcassette (1969 – )

Introduced by Olympus in 1969 for voice recording, the microcassette uses the same width of magnetic tape as the Compact Cassette (3.81mm) but in a much smaller shell. By using thinner tape and half or a quarter of the tape speed, microcassettes can offer comparable recording time to the Compact Cassette. The original standard microcassette, the MC60, gives 30 minutes recording per side at its standard speed of 2.4 cm/s, and twice the time at 1.2 cm/s.

Because of the format’s relatively low fidelity, microcassettes have mostly been used for recording voice, for example in dictation machines and telephone answering machines. However, it has also been used as a medium for computer data storage and music. In the early  1980s, some Walkman-type devices, and even some home audio players for stereo recording and playback were produced, and metal tape (equivalent to Type IV metal tape in Compact Cassettes) was available for higher fidelity.

Microcassette was more suited to data and music recording than the Mini-Cassette as the tape is pulled through by the capstan and has a more constant speed, whereas in the Mini-Cassette, the tape is pulled by the reels.

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Digital Compact Cassette (DCC) (1992 – 1996)

Digital Compact Cassette (DCC) was a digital audio recording format using magnetic tape, introduced by Philips and Matsushita in 1992. Pitched as a successor to Philips’ own Compact Cassette and competitor to Sony’s MiniDisc, it never became popular.

It shared the same form factor as compact cassettes, and DCC recorders could play back either type of cassette. This backward compatibility allowed users to adopt digital recording without rendering their existing tape collections obsolete.

As well as home players, portable and in-car players were produced.

Digital Compact Cassette was discontinued in October 1996 after Philips admitted it had achieved poor sales.

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Compact Cassette Type IV (Metal) (1979 – late 1990s)

The Type IV or metal-formulated Compact Cassette was introduced in 1979 by 3M under the trade name Metafine, and addressed a number of problems with previous tape formulations.

Standard Compact Cassettes (Type I or ferric-oxide) typically had poor high frequency definition, with pervasive tape noise (hiss). Type II (chromium dioxide) had much better frequency reproduction and very low noise but at the expense of some output level and low frequency solidity. Type III (ferro-chrome) was an attempt to restore some low frequency firmness but whilst Type III worked as a concept, it was not enough of an improvement to be taken up by the market.

Type IV was a completely new formulation using pure metal particles instead of metal oxides. This created a hard-wearing tape with superior frequency response and greater dynamic range.

It also had some disadvantages such as excess wear on tape heads, and they were expensive to buy. By the mid-1980s, metal tape did begin to catch on and was adopted by a lot of enthusiasts.

For tape recording equipment that was capable of using metal tape, there were extra indentations in the top of the cassette to identify it as Type IV and select the correct bias and equalization. On equipment without metal tape settings, it was possible to playback cassettes, but recordings would not be successful.

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Compact Cassette Type II (Chrome / High-Bias) (1970 – 2000s)

The Type II or chromium dioxide Compact Cassette was introduced to the market in 1970 by BASF.

Chromium dioxide provided an increase in high frequency response over the often rather muffled tone of the existing Type I ferric cassette, but took a while to take off as mainstream audio equipment available in the 1970s couldn’t make full use of the improvement in sound quality and it was only in the 1980s that chrome tapes become mass market.

Recording onto blank chromium dioxide tape ideally required the use of high-bias, and an EQ setting of 70μS. Pre-recorded music cassettes were often made to be played at 120μS (the same as ferric tape) to ensure wider compatibility.

An alternative formulation based around a cobolt / iron oxide was introduced in the mid-1970s and by the 1990s even BASF moved onto this substitute for chrome, although it was still labelled as chrome and was still high-bias.

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Streamer cassette (late 1980s – late 1990s)

Streamer cassettes were a variant of the Compact Cassette, specially designed for data storage (but different from standard cassettes used for data storage with early home computers) and had  a typical tape speed of 90 inches per second. Cassette tape streamers could be used with personal computers to make hard disk back ups.

They look almost identical to a normal Compact Cassette with the exception of a notch about ¼-inch wide and deep situated on the top edge of the cassette. Streamer cassettes also have a re-usable write-protect tab on only one side of the top edge of the cassette, with the other side of the top edge having either only an open rectangular hole, or no hole at all.

The whole of the ⅛-inch tape width is used for data, so there is only one ‘side’, but data is stored in four tracks in serpentine fashion.

Streamer cassettes could hold anywhere from 50 to 160 MB of data.

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Compact Cassette for data (1975 – late 1980s)

Early microcomputers often used punched tape for data storage, until in 1975 Jerry Ogdin and Les Solomon co-authored an article in Popular Electronics magazine about using inexpensive Compact Cassettes with audio tones to represent the binary data.

Many home computers of the late 1970s and early 1980s subsequently used cassettes for data storage as a cheaper alternative to paper tape or the floppy disks increasingly used in high-end microcomputers.

Typical speeds of loading were from 500 to 2000 bits per second, although some games used special, faster-loading routines, up to around 4000 bit/s. A rate of 2000 bit/s equates to a capacity of around 660 KB per side of a 90-minute tape.

Any type of Compact Cassette could be used, but smaller length cassettes such as C10 and C15 were produced for recording data.

Floppy disk storage become more prevelant by the mid-1980s, but cassettes remained popular for 8-bit computers such as the Commodore 64 and ZX Spectrum, particularly in the UK. Reliability of cassettes were variable, and multiple attempts to load programmes were sometimes required.

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DECTape II (1978 – early 1980s)

DECtape IIDECtape II was introduced around 1978 by Digital Equipment Corporation (DEC) for use in the TU58 tape drive, and was a specially formatted version of DC100.

DECtape II used 3.8 mm tape in a cassette format.

Like its predecessor, DECtape, a DECtape II cartridge had a capacity of about 256 kb. DECtape II cartridges could not be formatted by the end-user, and had to be purchased in a pre-formatted state.

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Endless loop Compact Cassette (1969 – 1990s)

Endless loop compact cassetteEndless loop cassettes are a variation of Compact Cassettes that play a continuous loop of tape without stopping.

They can range in length from 30 seconds upwards, and some include a sensing foil on the tape to allow tape players to re-cue. Uses include answering machines or musical jingles.

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Digital Audio Tape (DAT) (1987 – 2005)

Digital Audio Tape (DAT) was a digital magnetic audio tape format, initially designed for audio. It was introduced by Sony in 1987.

It used 4mm tape in a cassette, roughly half the size of a Compact Cassette. DAT tapes are between 15 and 180 minutes in length, a 120-minute tape being 60 meters in length.

The Recording Industry Association of America (RIAA) unsuccessfully lobbied against the introduction of DAT devices into the US, but a tax was imposed on DAT recorders and blank media from 1992.

It was never widely adopted by consumers due to its cost, but saw use in professional recording and as a data storage medium (called Digital Data Storage or DDS).

A small number of albums were commercially released on DAT in the first few years of the format.

In 2005, Sony discontinued its remaining DAT recorders.

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Compact Cassette (1963 – 2000s)

Compact Cassette (also known simply as cassette tape or tape) was a magnetic tape cassette format for audio, introduced by Philips in 1963. Compact Cassettes had two or four tracks (for stereophonic sound) and could be played in both directions.

On stereo cassettes, the two channels were adjacent to each other, making them compatible with mono-players and vice versa. Cassette tape was 3.81mm wide (often given as 4mm or ⅛ inch), and moved at 4.76 cm/s (1⅞ ips).

Different magnetic coatings were used, the original being ferric oxide (usually referred to as ‘normal’ or Type I). Chromium dioxide was introduced soon afterwards (usually referred to as ‘chrome’ or Type II), followed for a short time by a mixture of ferric-oxide and chromium dioxide (ferro-chrome or Type III) and later, pure metal particles were used (referred to as ‘metal’ or Type IV).

Notches on top of the cassette shell indicated the type of tape within. Type I cassettes had only write-protect notches, Type II had an additional pair next to the write protection ones, and Type IV (metal) had a third set in the middle of the cassette shell. These allowed later high-end cassette decks to detect the tape type automatically and select the proper bias and equalization.

All cassettes had a write protection tab that could be broken off to prevent accidental re-recording. By using a piece of adhesive tape, these could be covered to allow later recording.

Tape length usually was measured in minutes of total playing time. The most popular varieties of blank tape were C60 (30 minutes per side), C90, and C120. C90, and especially C120, used thinner tape which was more prone to stretching and breakage. Many other lengths were available, for example C15 for use for data recording.

Most cassettes used a tape leader, but for certain applications such as dictation, these were removed. There were also endless loop tapes available for applications such as answerphones.

It was originally designed for voice dictation use, but pre-recorded music cassettes were available from 1965, and as fidelity improved it became one of the predominant formats for pre-recorded music between the late 1970s and early 1990s.

Its success was partly due to the decision to freely license the format, and also due to its convenience over open reel tape.

It was additionally used for data storage for microcomputers in the late 1970s and 1980s.

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