| 摘要 |
PURPOSE:To eliminate the secular change of characteristics and the distortions of signals produced around a cut-off frequency, by using an A/D converter, plural non-cyclic digital filters and plural D/A converters. CONSTITUTION:The audio signals supplied from an input terminal 40 are converted into the digital signals by an A/D converter 41 and delivered to the non-cyclic digital filters 42-44. The filter 42 serves as a low pass filter and has a cut-off frequency fc1 and the filter 43 serves as a band pass filter with cut-off frequencies fc1 and fc2. Then the filter 44 serves as a high pass filter with a cut-off frequency fc2. These filters 22-44 have exactly same frequency characteristics and output level characteristics as those of the conventional low pass filter part, band pass filter part and high pass filter parts respectively. The outputs of filters 22-44 are converted into analog forms by the D/A converters 45-47 and delivered through output terminals 48-50. |
