| 摘要 |
PROBLEM TO BE SOLVED: To perform control to obtain a muted state instantaneously without increasing impedance of a mute circuit. SOLUTION: When performing control to change a demuted state to a muted state, first of all, a mute circuit 3 shifts from a non-attenuated state to an attenuated state to attenuate an audio signal by a predetermined attenuation amount using the mute circuit and then, an attenuation amount of a volume control means 2 is set to a maximum attenuation amount, thereby attenuating the audio signal by the maximum attenuation amount using the volume control means 2. Therefore, a level of pop noise, which may be generated in powering-on or selector switching, can be attenuated by the mute circuit. Since an audio signal is attenuated by the volume control circuit in a steady state, the attenuation amount of the mute circuit can be reduced, and impedance can be reduced. COPYRIGHT: (C)2009,JPO&INPIT
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