You would need to use a computer to play the files. I use a free program called Fobar2000 on a windows computer. The USB cable from the computer goes to a little usb to S/PDIF converter box. You run a digital cable from the converter box to the Alpha.
I looked into all of this when I got a new laptop with windows 10. The USB DAC I had was older and there were no windows 10 drivers. So I needed a converter that did not need drivers. In the end I felt it was easier just replace the DAC.
The Alpha is a good 30 years old. I think I would just get some type of streamer or USB DAC. I doubt it would hold up that well against a modern DAC. I can't remember what I replaced mine with. I do remember that I replaced the Delta with a used Theta Jade. The difference was night and day. Originally I had a CAL Tempest 2se which I loved. I lost it and got the Delta and Alpha to replace it. But I never felt they were as good.