Abstract: A problem is overcome in that when a signal is input and output in an analog signal format between two blocks for executing digital signal processing, a dynamic range is made improper by the dispersion of errors of the signal levels in a D/A converter and an A/D converter in the blocks. A gain is set such that the minimum value within the range of dispersion of errors of the signal level of a D/A converter 12 of a DSP 1 in a former stage is made larger than the maximum value within the range of dispersion of errors of the signal level of an A/D converter 21 in a latter stage. Then, the gain value of a second GCA 13 is set such that the level of a signal S5 is set to a maximum value within the range less than a prescribed value Vdr in a state that a signal having a level treated as a predetermined maximum value in the DSP 1 is input to the first GCA 13.

Abstract: A problem that when signal input/output is conducted in an analogue signal format between two portions processing digital signals, the dynamic range becomes inadequate due to error variations of signal levels of an internal D/A converter and A/D converter is solved. In a gain setting, firstly the magnitude relation is so set that a minimum value in a signal level error variation range of a D/A converter (12) in a front stage DSP (1) is greater than a maximum value in a signal level error variation range of an A/D converter (21) in a rear stage signal processing block. Secondly, in a state that a signal having the level handled as a predetermined maximum value in the DSP (1) is inputted to a first GCA (13), the gain value of the first GCA (13) is so set that the level of a signal S5 is the maximum in a range of below a prescribed value Vdr. Thirdly, the gain value of a second GCA (24) is so set that the level of the signal S5 is the maximum in a range of equal or less than a prescribed value.