To reduce the cost of devices, elements, etc. of an electronic volume 31 having a switching unit 32 and a volume unit 33 which adjust the signal level of analog signals obtained by the ΔΣ modulation, the amplitude amplification and the low-pass component extraction, thereby providing a desired level at a following digital amplifier 1.
Another switching unit 36, a volume unit 37, and a ΔΣ modulator 38 are provided. When small signals exist, data in one-bit signals ΔΣ-modulated by the ΔΣ modulator 38 and inputted to the switching unit 32 are signals of a small pulse density corresponding to the small signals. Thus, if offsets exist in the switching unit 32 and the volume unit 33 to restrain the attenuation quantity of the amplitude value, a sufficient attenuation of an output from a digital amplifier 1 can be obtained. This eliminates the need to cope with the offset and reduces the cost.
Ryuichi Kijima
Toru Enya
Ichiro Kaneko