Magnetic tape sound recording

Magnetic tape sound recording
Klaudia Wilde from the German WDR radio archive with a broadcast tape from 1990

The use of magnetic tape for sound recording originated around 1930. Magnetizable tape revolutionized both the radio broadcast and music recording industries. It did this by giving artists and producers the power to record and re-record audio with minimal loss in quality as well as edit and rearrange recordings with ease. The alternative recording technologies of the era, transcription discs and wire recorders, could not provide anywhere near this level of quality and functionality. Since some early refinements improved the fidelity of the reproduced sound, magnetic tape has been the highest quality analog sound recording medium available. However, as of the first decade of the 21st century, magnetic tape is largely being replaced by digital systems for most sound recording purposes.

Prior to the development of magnetic tape, magnetic wire recorders had successfully demonstrated the concept of magnetic recording, but they never offered audio quality comparable to the recording and broadcast standards of the time. Some individuals and organizations developed innovative uses for magnetic wire recorders while others investigated variations of the technology. One particularly important variation was the application of an oxide powder to a long strip of paper. This German invention was the start of a long string of innovations that have led to present day magnetic tape recordings.



Magnetic recording

Magnetic recording was conceived of as early as 1877 by the American engineer Oberlin Smith and demonstrated in practice in 1898 by Danish engineer Valdemar Poulsen. Analog magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves with a constant speed past a recording head. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal. A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal.

Early steel tape recorders

Early tape recorders were created by replacing the steel wire of a wire recorder with a thin steel tape. The first of these modified wire recorders was the Blattnerphone, created in 1929 or 1930 by the Ludwig Blattner Picture Corporation.

In 1931, Clarence N. Hickman of Bell Labs completed a prototype steel tape recorder based telephone answering machine. The machine saw limited use because AT&T policy forbade its use on public telephone lines.

On Christmas Day 1932 the British Broadcasting Corporation first used a tape recorder for their broadcasts. The device used was a Marconi-Stille recorder, a huge tape machine which used steel razor tape 3 mm wide and 0.08 mm thick. In order to reproduce the higher audio frequencies it was necessary to run the tape at 1500 millimetres per second past the recording and reproducing heads. This meant that the length of tape required for a half-hour programme was nearly 3 kilometres and a full reel weighed 25 kg. For safety reasons these machines would only be operated in a locked room by remote control. Due to the tape's speed, springiness and razor-like sharp edges, if the tape broke while in operation, it could unspool, fly off and cause serious injury. Besides this, the methods of recording could lead to massive data loss and poor audio quality because of their nature.

By the mid 1930s, the C. Lorenz company in Germany had developed a steel tape recorder that was briefly popular with European telephone companies and German radio networks. In 1938, Begun left Germany and joined the Brush Development Company in the United States, where work continued but attracted little attention until the late 1940s when the company released the very first commercial tape recorder in 1946: the Soundmirror BK 401. Several other models were quickly released in the following years. Tapes were initially made of paper coated with black oxide. Minnesota Mining & Manufacturing Company (3M) replaced them by plastic tapes in 1948.[dubious ][citation needed]

German developments

Magnetic tape recording as we know it today was developed in Germany during the 1930s at BASF (then part of the chemical giant IG Farben) and AEG in cooperation with the RRG. This was based on Fritz Pfleumer's 1928 invention of paper tape with oxide powder lacquered to it.

Engineers at AEG created the world's first practical magnetic tape recorder, the 'K1', and first demonstrated it in 1935. Eduard Schüller of AEG built the recorders and developed a ring shaped recording and playback head. It replaced the needle shaped head which tended to shred the tape. Friedrich Matthias of IG Farben/BASF developed the recording tape, including the oxide, the binder, and the backing material. Walter Weber, working for Hans Joachim von Braunmühl at the RRG, discovered the AC biasing technique, which radically improved sound quality.[1]

During World War II, the Allies noticed that certain German officials were making radio broadcasts from multiple time zones almost simultaneously.[1] Analysts such as Richard H. Ranger believed that the broadcasts had to be transcriptions, but their audio quality was indistinguishable from that of a live broadcast[1] and their duration was far longer than was possible with 78 rpm discs. In the final stages of the war in Europe, the Allied capture of a number of German Magnetophon recorders from Radio Luxembourg aroused great interest. These recorders incorporated all of the key technological features of modern analog magnetic recording and were the basis for future developments in the field.


American developments

Development of magnetic tape recorders in the late 1940s and early 1950s is associated with the Brush Development Company and its licensee, Ampex. The equally important development of the magnetic tape media itself was led by Minnesota Mining and Manufacturing (3M) corporation.

American audio engineer John T. Mullin and entertainer Bing Crosby were key players in the commercial development of magnetic tape. Mullin served in the U.S. Army Signal Corps and was posted to Paris in the final months of WWII. His unit was assigned to find out everything they could about German radio and electronics, including the investigation of claims that the Germans had been experimenting with high-energy directed radio beams as a means of disabling the electrical systems of aircraft. Mullin's unit soon amassed a collection of hundreds of low-quality magnetic dictating machines, but it was a chance visit to a studio at Bad Nauheim near Frankfurt while investigating radio beam rumours, that yielded the real prize.

Mullin was given two suitcase-sized AEG 'Magnetophon' high-fidelity recorders and fifty reels of recording tape. He had them shipped home[1] and over the next two years he worked on the machines constantly, modifying them and improving their performance. His major aim was to interest Hollywood studios in using magnetic tape for movie soundtrack recording.

Mullin gave two public demonstrations of his machines, and they caused a sensation among American audio professionals; many listeners literally could not believe that what they were hearing was not a live performance. By luck, Mullin's second demonstration was held at MGM studios in Hollywood and in the audience that day was Bing Crosby's technical director, Murdo Mackenzie. He arranged for Mullin to meet Crosby and in June 1947 he gave Crosby a private demonstration of his magnetic tape recorders.[1]

Bing Crosby's influence

Bing Crosby, a top movie and singing star, was stunned by the amazing sound quality and instantly saw the huge commercial potential of the new machines. Live music was the standard for American radio at the time and the major radio networks didn't permit the use of disc recording in many programs because of their comparatively poor sound quality. Crosby disliked the regimentation of live broadcasts 39 weeks a year,[1] preferring the recording studio's relaxed atmosphere and ability to retain the best parts of a performance. He had asked NBC to let him pre-record his 1944-45 series on transcription discs, but the network refused, so Crosby had withdrawn from live radio for a year. ABC agreed to let him use transcription discs for the 1946-47 season, but listeners complained about the sound quality.[1]

Mullin's tape recorder came along at precisely the right moment. Crosby realised that the new technology would enable him to pre-record his radio show with a sound quality that equalled live broadcasts, and that these tapes could be replayed many times with no appreciable loss of quality. Mullin was asked to tape one show as a test and was immediately hired as Crosby's chief engineer to pre-record the rest of the series.

Crosby's season premier on 1 October 1947 was the first magnetic tape broadcast in America.[1] He became the first major American music star to use tape to pre-record radio broadcasts, and the first to master commercial recordings on tape. The taped Crosby radio shows were painstakingly edited through tape-splicing to give them a pace and flow that was wholly unprecedented in radio. Mullin even claims to have been the first to use "canned laughter"; at the insistence of Crosby's head writer, Bill Morrow, he inserted a segment of raucous laughter from an earlier show into a joke in a later show that hadn't worked well. Tape's high audio quality caused other radio performers to demand the ability to prerecord their broadcasts, forcing an end to the recording ban.[1]

Keen to make use of the new recorders as soon as possible, Crosby invested $50,000 of his own money into the Californian electronics company Ampex, and the tiny six-man concern (headed by Alexander M. Poniatoff, whose initials became part of the company name) soon became the world leader in the development of tape recording, revolutionising radio and recording with its famous Model 200 tape deck, issued in 1948 and developed directly from Mullin's modified Magnetophones.

Standardized products

Working with Mullin, Ampex rapidly developed two-track stereo and then three-track recorders. Spurred on by Crosby's move into television in the early 1950s, Ampex had developed a working monochrome videotape recorder by 1956 and later a color recorder, both created to tape Crosby's TV shows.

The typical professional tape recorder of the early 1950s used ¼" wide tape on 10½" reels, with a capacity of 2400 feet (730 metres). Typical speeds were initially 15 in/s (38.1 cm/s) yielding 30 minutes' recording time on a 2400 ft (730 m) reel. 30 in/s (76.2 cm/s) was used for the highest quality work. Domestic and portable recorders used seven, five or even three inch reels (or spools). Early professional machines used single sided spools but double sided spools soon became popular (particularly for domestic use). Tape spools were usually made from transparent plastic but metal spools were also used.

Standard tape speeds varied by factors of two — 15 and 30 in/s were used for professional audio recording; 7½ in/s (19 cm/s) for home audiophile prerecorded tapes; 7½ and 3¾ in/s (19 and 9.5 cm/s) for audiophile and consumer recordings (typically on 7 in or 18 cm reels). 1⅞ in/s (4.76 cm/s) and occasionally even 15/16 in/s (2.38 cm/s) were used for voice, dictation, and applications where very long recording times were needed, such as logging police and fire department calls.

The 8-Track tape standard, promoted by Bill Lear in the early 1960s, popularized consumer audio playback in automobiles. Eventually, this standard was replaced by the smaller and more reliable Compact Cassette.

Philips' development of the Compact Cassette in 1963 and Sony's development of the Walkman in 1979 [2] led to widespread consumer use of magnetic audio tape. In 1990, the Compact Cassette was the dominant format in mass-market recorded music.[3] The development of Dolby noise reduction technology in the 1960s brought audiophile quality recording to the Compact Cassette also contributing to its popularity.

Innovative uses

Magnetic tape brought about sweeping changes in both radio and the recording industry. Sound could be recorded, erased and re-recorded on the same tape many times, sounds could be duplicated from tape to tape with only minor loss of quality, and recordings could now be very precisely edited by physically cutting the tape and rejoining it.

Within a few years of the introduction of the first commercial tape recorder, the Ampex 200 model, launched in 1948, American musician-inventor Les Paul had invented the first multitrack tape recorder, bringing about another technical revolution in the recording industry. Tape made possible the first sound recordings totally created by electronic means, opening the way for the bold sonic experiments of the Musique Concrète school and avant garde composers like Karlheinz Stockhausen, which in turn led to the innovative pop music studio recordings of artists such as Frank Zappa, The Beatles and The Beach Boys.

Tape enabled the radio industry for the first time to pre-record many sections of program content such as advertising, which formerly had to be presented live, and it also enabled the creation and duplication of complex, high-fidelity, long-duration recordings of entire programs. It also, for the first time, allowed broadcasters, regulators and other interested parties to undertake comprehensive logging of radio broadcasts for legislative and commercial purposes, leading to the growth of the modern media monitoring industry.

Innovations like multitrack recording and tape echo enabled radio programs and advertisements to be pre-produced to a level of complexity and sophistication that was previously unattainable and tape also led to significant changes to the pacing of program content, thanks to the introduction of the endless-loop tape cartridge.

See also


External links

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