PURPOSE: To reduce the current distortion and at the same time to improve the mass productivity for the titled magnetic circuit, by using a sintered metal of a magnetic powder material for a part or whole of a yoke, a pole piece, a top plate, etc. which constitute the magnetic circuit.

CONSTITUTION: A magnetic powder material such as iron, etc. is coated by plating with a nonmagnetic metal such as copper, silver, etc. having higher conductivity than said magnetic powder material. Such a powder metallurgic material coated with a metal is sintered to obtain a sintered magnetic material. This sintered metal is used to a top plate 4' and a pole piece part 5'1. As a result, each sintered magnetic particle is short-ringed like a copper cap and functions as a single magnetic domain unit to eliminate the AC magnetic flux generated by an audio current. Thus the hysteresis loss is reduced.