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THE FIRST practical magnetic recorder was the "Telegraphone" invented by Poulsen in Denmark as long ago as 1890. Experimenters had been using machines that recorded on iron wire for at least thirty years before that but they were unreliable, Rube Goldberg contraptions giving poor results. Poulsen's Telegraphone was surprisingly good mechanically but the biggest improvement was the use of a special steel wire that had a lower distortion and better signal-to-noise ratio than possible with ordinary iron wire. It was eventually made under license in America and Europe and by all accounts was quite successful. Steel wire was used in these and other recorders for the next thirty years or so although there were, of Bourse; continual improvements in the magnetic characteristics with the employment of new alloys and better methods of manufacture. Examples of wire recorders used by broadcasting authorities in the 1930s include the Blattnerphone in Germany and the Marconi-Stille in England. This latter machine, used quite extensively by the BBC, had large metal reels that could accommodate 10,000 feet of tungsten steel tape. These reels, as you might expect, were very heavy and it took two men to lift one! Not the sort of machine to carry around.... A big step forward was use of bias, that is the introduction of a high frequency voltage superimposed on the recording signal to reduce distortion. The basic principles were formulated by Carlson in 1921, who took out further patents in 1927.
Wire recorders were produced in this country until the late 1940s when they were supplanted by machines using coated tapes. This idea was not new--in fact one Mberlin Smith suggested the use of cotton or silk tapes impregnated with magnetic particles as far back as 1888. Of course, it was quite impractical (what could you expect from a man with a name like Mberlin?) and it was many years before all the problems were solved. Well, most of them. In 1928, Pflaumer in Germany took out a patent covering a method of coating paper or plastic tape with magnetic material and a few years later the German AEG-Telefunken company brought out the "Magnetophone," the first commercial tape recorder.
During the war, German scientists made considerable progress with the development of tape recorders and special oxides suitable for tape coating. After the war, these tape recorder inventions were brought to the attention of several American companies who were not impressed. They said the equipment was not practical, it was cumbersome, the tape could be broken too easily, and so on. However, one engineer who was more far-sighted was Alexander Poniatoff who had formed the Ampex company in 1944. He was so convinced of the future of tape recording that he immediately switched his company-then consisting of 27 people--over to development work in that field.
One year later, in 1947, he demonstrated the famous Model 200, a professional machine intended for broadcasting applications. As he remarked later, "This was the beginning of the new era in magnetic recording in America." Although he was referring to the broadcasting aspect, his words could have applied equally well to tape recording as a whole.
Since then we have seen many refinements and inventions such as multi tracks, ferrite heads, chromium-dioxide tape, videotape, the Dolby system, and cassettes. At one time-not so long ago--it was necessary to use tape speeds of 15 or even 30 ips for high fidelity reproduction, but this requirement fell to 7 1/2 and now 3 3/4 ips--which of course, gives longer playing time.
Cassette recorders playing at 17/8 ips were not even considered medium-fi two short years ago but they are improving rapidly, and there are now several machines on the market claiming a response up to 15 kHz with low distortion. However, at the present state of the art, open-reel recorders are still superior in terms of fidelity-which takes into account wow and flutter as well as frequency response, distortion, and signal-to-noise ratio.
The specifications presented in the following pages are in tabular form which was first used in 1965 to facilitate comparisons. Readers should bear in mind that these specifications are those supplied by the makers-they are not the result of our tests or measurements. Methods of measurement vary from manufacturer to manufacturer but in general the figures are compatible.
Obviously, not all available recorders are listed. Some manufacturers did not supply us with the necessary information, and some products had to be omitted due to space limitations.
For a directory of tape recorder manufacturers, see page 61. (adapted from Audio magazine, Jan. 1971)
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