For flat frequency response of record and replay mode, audio magnetic tape recorders are provided with a high frequency bias current adjusting system and also a frequency characteristic adjusting system. These adjusting systems have come to be necessary because a variety of magnetic tape characteristics have been developed by a number of different tape manufacturers. Tape recorders in this domestic market are equipped with the pre-set tape selector to select the optimum bias current to each tape for use and to choose the correct position of recording current equalizer. It is most desirable to adjust the bias and the recording equalizer depending on the characteristic of individual tape for use, but the procedure is rather hard for consumers in general in the domestic market as it requires some special instruments such as audio frequency oscillator, voltmeter, and others. Proper seeing of magnetic tape with the optimum bias current is another serious problem for hi-fi recording. Intending to solve these problems, we have developed special tape recorder circuits. The special system we have developed has two stages, the one is the automatic bias current adjusting circuit, and the other is the automatic recording equalizer adjusting circuit. The time required to complete the adjustments is about 20 seconds. The optimum values of bias current and recording equalizer are memorized by Analog Memory, the device newly developed. Examples of practical applications to professional type of tape recorders are given in article to follow.
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