With the implementation of the OptiBus®USB digital input, all music content (including WAV, AAC, WMA, MP3 etc.) stored on the ever more ubiquitous personal computer can finally be played back through the CD-77 in their full glory. In addition, with the ever increasing storage capacity of the personal computer, it is now possible to turn a personal computer into an audiophile jukebox with storage capacity of hundred of CDs without any loss of sound quality. Using the more common S/PDIF digital connection to connect a personal computer to an outboard DAC was deemed unacceptable to AMR because of the high levels of jitter presented in the S/PDIF digital connection. This is the same reason why the provision of either S/P-DIF digital outputs or inputs on the CD-77 was rejected at the outset.

The specially designed ultra-low jitter OptiBus®USB digital input is an interface between the personal computer and the CD-77. Due to its isosynchronous nature the USB interface, as compared to the serial S/P-DIF or AES/EBU protocol, it offers much lower levels of jitter. Unfortunately many common implementations of USB receiver chips do not take advantage of this.