PURPOSE: To perform the best mixing with simple constitution by connecting a pulse code modulation (PCM) recording system to a PCM reproduction system with a multicontact change-over switch by way of a digital mixer and digital attenuator.

CONSTITUTION: Change-over switch S1 is placed at fixed contact C and an analog signal to be mixed is supplied to input terminal IN. Then, a reproduced digital signal obtained by PCM reproduction system 19 and the digitized signal of a mixing signal are mixed digitally by digital mixer (adder) 22 at a proper level by way of digital attenuator 23 and the mixture is recorded by digital recording (reproducing) device 16 by way of PCM recording system 15, thereby performing desired digital mixing. In this case, when change-over switch S2 is placed at fixed contact B, the analog output of the digitally mixed signal can be obtained as a monitor signal at terminal OUT and when at fixed contact A, that of PCM reproduction can be obtained at terminal OUT. Thus, the best mixing is carried out.