| 摘要 |
PURPOSE:To control the signal level without changing a presence of a stereo signal by managing an ALC level based on a detection voltage signal for a channel with a larger level in input stereo sound signals for the left and right channels. CONSTITUTION:Left and right channel signals Lin, Rin in stereo audio signals are passed respectively through voltage controlled amplifiers 3,4 and detected by detection circuits 5, 6. The detection output is fed to a base of transistors(TRs) 7a, 7b of a voltage selection circuit 7. The selection circuit 7 passes a detection voltage signal with a larger level in two detection voltage signals and the result is fed back to amplifiers 3, 4 as a level control voltage signal. The ALC level is set by a detection voltage and the amplifiers 3, 4 controls the level of the audio input signal based on the level control voltage signal and outputs audio outputs Lout, Rout of left and right channels after the suppression of the level. Thus, the level control in which the presence of the stereo signal is unchanged is attained. |
