To make it possible to cancel noise or a hum effectively without sacrificing sound quality by reduction coupling coils inductively and magnetically with each other by a shield.

A lower coil 20 extends to the circumference of magnetic pole pieces 13-18 and is positioned between plates 11 and 19. The shield 21 has a web 22 and two opposite downward wall surfaces 23 and 24. Further, an upper coil 30 is provided between plates 31 and 32. The plates 31 and 32 have an opening 33 for receiving the magnetic pole pieces 34-39. Then the shield 21 equipped with a web 41 and opposite wall surfaces 42 and 43 separate the coil 30 magnetically from the coil 20 together with the shield 21. Further, the wall surfaces 23 and 24 of the shield 21 extend downward onto the flank of the lower coil 20 and the wall surfaces 42 and 43 of the shield 40 extend upward onto the flank of the coil 30.