PURPOSE: To obtain a stable noise reduction circuit where the phase rotation in a filter is restrained, by saturating the attenuation characteristic of low-pass and high-pass filters halfway.
CONSTITUTION: When switches 28 and 29 are connected as shown in the figure, input signals from terminal 1 are outputted to terminal 2 through amplifier 27. Low-pass filter 30, high-pass filter 31 and variable gain elements 24 and 25 controlled level sensors 5 and 14 are provided on the feedback path for amplifier 27. As a result, signals from terminal 1 have bands divided and have their levels subjected to logarithmic compression and are outputted to terminal 2 and used as sound recording signals for a tape recorder, etc. Low-pass and high-pass filters are constituted by resistances and capacitors as shwon in the figure, and their attenuation characteristic is saturated halfway, and the phase rotation is restrained to 90° or less. When switches 28 and 29 are switched, signals from terminal 1 are expanded.
NISHIMURA MASARU
SHIMIZU TETSUO
SATOU KENICHI
