| 摘要 |
PURPOSE:To obtain a clear and crisp output by providing respectively a switch turning on/off simultaneously a power supply and an input signal system of an amplifier to the both. CONSTITUTION:Control signals A', B', C; are kept logical '1' normally, and analog switches 3 are all opened in this state and input signals A, B, C are not inputed to an amplifier 4. On the other hand, the level of an AND gate 2 is logical '1', a high level, then a control circuit 1 of an amplifier power is turned off and no power is fed to the amplifier 4. In desiring to amplify, e.g., the input signal A, when the level of the control signal A' is brought to logical 0, an analog switch 3 corresponding to the input signal A is close, the input signal A is inputed to the amplifier 4 and the AND gate 2 goes to logical 0 output, a low level output, the control circuit 1 for the amplifier power supply is turned on and power is fed to the amplifier 4. Since a noise at no signal is not amplified, a clear and crisp sound is outputted.
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