| 摘要 |
PROBLEM TO BE SOLVED: To provide a device for adding an audio signal, reducing overall noise level even when multiple terminals are prepared for inserting multiple microphone plugs thereto. SOLUTION: In the device 1 for adding an audio signal, when no microphone plug 1000 is inserted, the gain of an amplifier circuit in its input stage 10 can be reduced from (R1+R2)/R1 to 1, whereby the output noise level Vn can be remarkably reduced as the number of input terminals where no microphone plug is inserted is increased, thereby increasing the S/N ratio of an audio signal. COPYRIGHT: (C)2010,JPO&INPIT
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