| 摘要 |
PURPOSE:To suppress noise and to obtain good sound quality, by using an expander so as to decrease an output level when an input level is small. CONSTITUTION:An input terminal 22 is connected to an output of a transmission system 18 and an output terminal 29 is connected to a VCA19, respectively. The time constant is determined by an input resistor 23, an output resistor 28 and a capacitor 27. The inclination of the expanding characteristics is increased more as the input level is smaller from nearly -30dB, the ratio of expansion is increased and this characteristic depends on the value of a voltage V and the time constant. When the input level x1 to the compressor is as x1>-60dB, the relation of x1=x2 (expander output level) is obtained and the level is restored to the original level. With x1<-60dB, the relation of y2<y1 is obtained, the compander output is smaller than the input level and the noise is suppressed. |
