You get a USB to SPDIF converter. Streamers always start with an asynchronous data stream, USB. This is the way information is exchanged in the computer world. The question is where the stream is clocked for music. It can be clocked in the streamer, or in the DAC, or as in my case, a very trick master clock.
Moon Audio and Arrender make really nice converters. The best is the Berkeley Alpha USB. I have one, but I do not use it any more as I have a master clock