History of Sound Recording - Magnetic Recording

Magnetic Recording

Magnetic recording was demonstrated in principle as early as 1898 by Valdemar Poulsen in his telegraphone. 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.

With the addition of electronic amplification developed by Curt Stille in the 1920s, the telegraphone evolved into wire recorders which were popular for voice recording and dictation during the 1940s and into the 1950s. The reproduction quality of wire recorders was significantly lower than that achievable with phonograph disk recording technology. There were also practical difficulties, such as the tendency of the wire to become tangled or snarled. Splicing could be performed by knotting together the cut wire ends, but the results were not very satisfactory.

On Christmas Day, 1932 the British Broadcasting Corporation first used a steel tape recorder for their broadcasts. The device used was a Marconi-Stille recorder, a huge and dangerous machine which used steel razor tape 3 mm (0.1") wide and 0.08 mm (0.003") thick running at 90 metres per minute (approximately 300 feet per minute) past the recording and reproducing heads. This meant that the length of tape required for a half-hour programme was nearly 3 kilometres (1.9 mi) and a full reel weighed 25 kg (55 pounds).