spdif Output to DAC/Headphone Amp?

[FreeBlues]

I assume this is possible, but I can't make it work. I want to output my 11R to a stand alone dac, then run that signal into a dedicated headphone amp. Seems like it should be easy, but I'm not having any success.

So, using the 11R as a standalone source (not connected to my computer), I plug my guitar into the 'Guitar Input', connect a coax spdif cable to the 'Output" on the back of the 11R, set the 'User Options' for 'Digital Output' to 'Rig Outputs', connect the spdif cable to my dac then to my headphone amp, think I'm done. No signal through my dac.

Am I missing something? This same setup works just fine using my M-Audio FireWire Solo as the guitar input (connected to the computer and using S-Gear). Are there other settings I need to make on the 11R?