Tape recorder
An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present-day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal. Tape-recording devices include the reel-to-reel tape deck and the cassette deck, which uses a cassette for storage.
This article is about machines used for audio (sound) recording. For video recording, see video tape recorder. For the tape systems used for computer data, see tape drive.
The use of magnetic tape for sound recording originated around 1930 in Germany as paper tape with oxide lacquered to it. 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 other recording and broadcast standards of the time. This German invention was the start of a long string of innovations that have led to present-day magnetic tape recordings.
Magnetic tape revolutionized both the radio broadcast and music recording industries. It gave 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 recording medium available. As of the first decade of the 21st century, analog magnetic tape has been largely replaced by digital recording technologies.
Commercialization[edit]
American developments[edit]
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 medium itself was led by Minnesota Mining and Manufacturing (3M) corporation.
In 1938, S.J. 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 consumer tape recorder in 1946: the Soundmirror BK 401.[15] Several other models were quickly released in the following years. Tapes were initially made of paper coated with magnetite powder. In 1947/48 Minnesota Mining & Manufacturing Company (3M) replaced the paper backing with cellulose acetate or polyester, and coated it first with black oxide, and later, to improve signal-to-noise ratio and improve overall superior quality, with red oxide (gamma ferric oxide).[28]
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[26] 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 heard 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.[26]
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,[26] preferring the recording studio's relaxed atmosphere and ability to retain the best parts of a performance. He asked NBC to let him pre-record his 1944–45 series on transcription discs, but the network refused, so Crosby withdrew 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.[26]
Crosby realised that Mullin's tape recorder technology would enable him to pre-record his radio show with high sound quality 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 subsequently 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.[26] 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.[b] Soon other radio performers were demanding the ability to prerecord their broadcasts with the high quality of tape, and the recording ban was lifted.[26]
Crosby invested $50,000 of his own money into the Californian electronics company Ampex, and the 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, with its Model 200 tape deck, released in 1948 and developed from Mullin's modified Magnetophons.
Since their first introduction, analog tape recorders have experienced a long series of progressive developments resulting in increased sound quality, convenience, and versatility.
Operation[edit]
Electrical[edit]
Due to electromagnetism, electric current flowing in the coils of the tape head creates a fluctuating magnetic field. This causes the magnetic material on the tape, which is moving past and in contact with the head, to align in a manner proportional to the original signal. The signal can be reproduced by running the tape back across the tape head, where the reverse process occurs – the magnetic imprint on the tape induces a small current in the read head which approximates the original signal and is then amplified for playback. Many tape recorders are capable of recording and playing back simultaneously by means of separate record and playback heads.
Limitations[edit]
The storage of an analog signal on tape works well, but is not perfect. In particular, the granular nature of the magnetic material adds high-frequency noise to the signal, generally referred to as tape hiss. Also, the magnetic characteristics of tape are not linear. They exhibit a characteristic hysteresis curve, which causes unwanted distortion of the signal. Some of this distortion is overcome by using inaudible high-frequency AC bias when recording. The amount of bias needs careful adjustment for best results as different tape material requires differing amounts of bias. Most recorders have a switch to select this.[c] Additionally, systems such as Dolby noise reduction systems have been devised to ameliorate some noise and distortion problems.
Variations in tape speed cause wow and flutter. Flutter can be reduced by using dual capstans. The higher the flutter the more noise that can be heard causing the quality of the recording to be worse.[35] Higher tape speeds used in professional recorders are prone to cause head bumps, which are fluctuations in low-frequency response.[36]