I believe the standard way to connect a line-in audio source to the BS5 is through a Behringer device that converts analog audio to USB.  However, I'm thinking about connecting a Core to my BS5, and the Core also has digital output so why not use it? I've found this device on the interweb that claims to do exactly this (https://hifimediy.com/product/hifime-ur23-spdif-optical-to-usb-converter/).  Any reason why this wouldn't not work?  I'm not really up to date on digital audio formats. Thanks in advance.