A Syba adaptor will convert any USB output to optical. They cost less than $10. I have one and it works just fine driving an optical input on an Emotiva XDA-2.
https://www.amazon.com/External-Ada...ywords=syba+external+usb+stereo+sound+adapter
Likely jittery, but the Emotiva has a reclocker, while works well for you it may not work as well in all cases .