The specifications and manual mention that the S/PDIF optical input is only pass-through, yet it shows up as an input in Windows 10 and you can record just fine with software such as Audacity.' However I still can't tell you if digital audio input will be output from USB when the C5 DAC is connected. So it won't do 24 Bit or 96 KHz or any of that. The C-Media Audio chip in this device is quite basic, limited to 16 Bit and 48 KHz. One recent review on Startech's website says the following 'I wasn't interested in the 7.1 features, but more for recording purposes, especially the optical input. Maybe I'm wrong about the Startech device. Music copyright holders don't want us to be able to record digital audio input. I suspect that all or nearly all current external sound cards are made to prevent the computer itself from receiving digital audio input. [Edit}So, after further inspection, it appears that the Startech device won't do what you want. Note that the Startech device's SPDIF optical pass-through port (optical input) supports only two-channel audio. Example: My suspicion is that these external cards only allow using their own outgoing connections for audio output and would not allow using a USB connection on the PC for audio output. Since theres bo other way or an adapter that does that There are eternal USB sound cards with optical audio in. Then have laptop receive it from toslink then output from usb as usual. What if i get a toslink adapter for laptop so it can act as an intermediary device.

Video digital optical converter