| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the control of dispersion for each of magnetic heads. SOLUTION: The output voltage of the magnetic head 6 is supplied via a capacitor 14 to an output-controllable amplifying circuit 16 for gain control, and the output, after being processed by an output-controllable adding circuit 18 for offset control, is supplied via an A/D converter 20 to a controller 24, as a magnetism quantity detection signal Dm. The controller 24 switches applied voltage and controls the amplifying circuit 16 and the adding circuit 18, applies DC voltage to the magnetic head 6 and controls the adding circuit 18 so that the magnetism quantity detection signal Dm at this time is at a reference value, and applies AC voltage to the magnetic head 6 and controls the amplifying circuit 16 so that the amplitude of the magnetism quantity detection signal Dm is a reference amplitude.
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