So the ua5 needs to be modified to send optical or coax signal out?
If so why are those outputs there from the factory?
Yes, it needs to be modified to use the optical or coax outputs in "standalone" mode, i.e. without a computer hooked up. Those outputs exist, in stock form, so one may play back/monitor from the computer: computer > USB > UA5 > coax/optical out.
If you're a DIY type, or know someone who is, there are instructions around somewhere for how to do the mod yourself.
Edit to add: UA5 digi-mod instructionsEdit to add again: alternatively, you could send it to Busman Audio to have it modded (if he's still modding UA5s).