Getting digital audio into 2017 iMac through USB port

I am currently transferring some old audio tapes into digital format by using the PreSonus Audiobox USB96 and Audacity. This is working just fine when feeding analog signals to the Audiobox, which converts them to digital and sends them to the iMac via the USB port. However I also want to send some digital output straight from a CD player to Audacity on the iMac, bypassing the Audiobox. Is this as simple as getting a SPDIF to USB dongle of some sort? Seems like the ones I see on Amazon are only for output from the iMac, not for input. Are there two-way versions? Is there any extra conversion needed for digital output from a CD player?