| 摘要 |
PROBLEM TO BE SOLVED: To avoid clipping a mixing amplifier and prevent the S/N ratio from deteriorating due to the amplifier, when the sound volume balance of a plurality of audio signals is held at an appropriate level. SOLUTION: Audio signals inputted to a plurality of input terminals 21<SB>1</SB>-21<SB>n</SB>are led to a mixing amplifier via their respective lines of series connected variable resistors 22<SB>1</SB>-22<SB>n</SB>, selective switches 23<SB>1</SB>-23<SB>n</SB>and mixing resistors 24<SB>1</SB>-24<SB>n</SB>. The mixing amplifier 25 mixes them to output. The gain of the mixing amplifier 25 is variably controlled by operating a volume control 26. The gain of the amplifier 25 is raised to hold the S/N ratio high for a small number of audio signals to be outputted. The gain of the amplifier 25 is lowered to avoid clipping the audio signals for a large number of audio signals to be outputted. COPYRIGHT: (C)2004,JPO
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