PURPOSE: To detect the azimuth of a magnetic head by utilizing a signal of music, etc., recorded on the same sound recording track of a magnetic tape.

CONSTITUTION: Reproduced signals led out of coil groups 13 and 13' are passed through regenerative amplifier circuits 14L and 14'L and synthesized to be outputted from an audio output terminal 15L as a left-channel audio reproduced signal. It is inputted to a differential amplifier 17 through high-pass filters 16 and 16' which eliminate low frequency components influenced by counter effect. The output differential signal of two inputs is outputted by the differential amplifier 17 is inputted to a phase detector 18 which detects the phase of the input signal on the basis of the zero-cross point of the audio reproduced signal. The output of this detector 18 is inputted to a motor driving circuit 20 as a control signal for controlling an azimuth adjusting motor 21 which drives an adjusting member such as an azimuth adjusting screw for varying the azimuth of a reproducing head.