| 摘要 |
PURPOSE:To quicken starting of muting action and to suppress outputting action of noise signals surely by starting muting action at the time of applying and breaking of a power source by utilizing the voltage of the input side of a constant voltage circuit. CONSTITUTION:The DC voltage rectified and smoothed by a rectifying and smoothing circuit 11 is made constant by a constant voltage circuit 14 and supplied to a pre-amplified circuit 2 and a main amplifier circuit 4. When a power source switch 9 is closed, such action is made and power is supplied, and the voltage of an output terminal A of the rectifying and smoothing circuit 11 rises quicker than the voltage of an output terminal B of the constant voltage circuit 14. Accordingly, when the power source switch 9 is closed, a charge current flows from the output terminal A of the rectifying and smoothing circuit 11 to a capacitor 20 through a Zener diode 21 and a non-return diode 22, and the capacitor 20 is charged at once. When the capacitor 20 is charged, operating power is supplied from the charging terminal to the first NAND circuit 24 and the second NAND circuit 25 that constitute an inversions circuit 23. |
