| 摘要 |
A bias current setting apparatus is used in a magnetic recording and reproducing apparatus having a bias current supplying circuit and a magnetic head for recording an audio signal with the bias current on a magnetic tape. The bias current setting apparatus comprises an oscillator for oscillating signals of different frequencies, said signals of different frequencies being recorded and reproduced on and from the magnetic tape in the magnetic recording and reproducing apparatus, a circuit for varying the current value of the bias current, a first detector for detecting the signal of different frequencies which have been recorded and reproduced, a filter for separating a harmonic component of the signal of a frequency which have been recorded and reproduced, a second detector for detecting the output signal of the filter a converter for converting the output signals of the first and second detector which have been selectively supplied thereto into digital signals, and a computer for controlling the bias current setting circuit with a stored program system responsive to the digital signals supplied from the converter thereby varying the bias current value and setting the same at a current value appropriate to the recording on the magnetic tape. The computer varies and sets the bias current value so that the levels of the signals of different frequencies detected by the first detector fall within the predetermined frequency characteristic specification range and distortion factor measured responsive to the output signals of the first and second detectors falls within the predetermined distortion factor characteristic specification range.
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