DAC connection issues (1 Viewer)

I just got a cheapy run of the mill dell desktop to use as a media server and to do my homework with. I had an extra USB DAC laying around, which is the JDS Labs ODAC. It has a 2.5mm spdif out, but my yamaha receiver only has optical, coax, and HDMI digital ins. So what I tried to do as solution is to use a SPDIF to coax adapter installed on the end of a regular RCA cable and run it as the cable that connects the computer audio to the receiver.
Its not working. I've already changed the default audio device to the DAC, and the computer is seeing it being plugged in. I currently have the HDMI running video to my tv via the receiver, and the USB DAC running the audio from the SPDIF out on the dac, to the simple little plug in converter to the coax in on the receiver. Any ideas what the problem could be?