| 摘要 |
PURPOSE:To improve the S/N and to attain the synthesis of a signal which is made to uniform level by adjusting automatically an input level of a mixing circuit in response to a signal level and applying muting control in response to the input level. CONSTITUTION:The signal from the signal sources 21-2N is given to the 2nd amplifiers 141-14N via the 1st amplifiers 61-6N, its output is rectified and smoothed by a diode 22 and a capacitor 24 so as to control the impedance of electronic volume circuits 261-26N, resulting that the input level of the 2nd amplifiers 141-14N is adjusted and a signal with arranged levels is outputted from the 2nd amplifiers 141-14N. On the other hand, an output of the 1st amplifiers 61-6N is given to muting circuits 161-16N after being rectified and smoothed by a diode 18 and a capacitor 20, muting circuits of a system where no input signal is given is interrupted so as to prevent an unnecessary noise from being inputted to a mixing circuit 8. Thus, the signal of the system where the input signal exists is inputted to the mixing circuit while its level is arranged. |
