The s/pdif digital out can be used to bypass the internal DAC of the CD-6 and send a digital signal to an outboard DAC or processor, should you wish to use a different D to A device. A great many of the current external DACs do specific de-jittering and reclocking of the digital signal which could lead to better quality than using the CD-6 with its own internal DAC. I say "could" because I have no experience with the CD-6 and it may well be that this player already has excellent clocking and de-jittering circuitry.