PURPOSE: To obtain an A/D converting device that requires no high-speed converter by using two systems of multiplexer MX circuits and by assigning one for analog signals for right and left channels CH and the other for range discrimination.

CONSTITUTION: In the PCM recorder, left and right CH analog signals are inputted to input terminals 30 and 31 and sampled and held S/H 32 and 33 with sampling pulses from control pulse generation part 42 before being supplied to MX circuit 34. Through switches S1 and S2 of circuit 34, S/H-ed left and right CH sampled signals are changed over sequentially synchronizing with control pulses from control part 42 and sent to attenuator ATT35 and range detecting circuit 36. The signal range- detected by circuit 36 is stored in latch circuit 38 and signals, corresponding to left and right CHs, from circuit 38 are supplied to ATT35 via OR circuit 40 to control the attenuation of ATT35. The sampled signal from ATT35 is A/D-converted 12 and sent to the PCM recording system together with sorting data from circuit 38.