| 摘要 |
PURPOSE:To prevent generation of an abnormal sound, by connecting a muting transistor between an earth terminal of a connecting jack and an earth, and controlling by turning on and off of this transistor by the voltage at both ends of a capacitor prepared for eliminating the ripple of a power supply. CONSTITUTION:At the moment when an electric power source switch 13 is turned on, a current flowing to a driving motor 12 is large, and a current flowing to capacitors 14a, 14b is also large, therefore, an electric power supply ripple appears very greatly. In this state, since the capacitors 14a, 14b are not charged yet sufficiently, both transistors 9, 8 are in an off-state. Accordingly, a large output by an electric power supply ripple appearing in the output end of amplifying circuits 2a, 2b is not applied at all to an earphone and a head phone. When the electric power source switch 13 is turned on and a constant interval of time elapses, the amplifying circuits 2a, 2b enter into a normal operating state, respectively, also the transistors 9, 8 are turned on, respectively, and outputs of the amplifying circuits 2a, 2b are applied to the earphone and the head phone. |
