| 摘要 |
PURPOSE:To avoid the trouble of a switching operation and to improve the S/N. CONSTITUTION:A sense circuit 13 senses the input of a B-channel audio signal, especially, the presence of ground of a ground terminal of an input side of an isolator, the audio signal of a channel A is fed simultaneously to a B-channel when the signal ground of the B channel is open, amplifiers 11a, 11b and 12a, 12b are fully driven regardless of one input as 4-channel outputs. Thus, in the case of 1-input 4-channels, the sense circuit 13 senses the presence of the connection of the B channel to turn on switches 14a, 14b of an analog switch 14, then it is not required to make the switching of changeover switches 7-10 by manual operation different from a conventional switching circuit. |
