Unitiserve output question

The user manual advises to connect ONE of the coax or optical audio outputs.  Other than that, I'm not sure what you're trying to do with two outputs from one player.  Are you trying to play two cd's at once?  Or feed two systems from a single player (playing the same cd)?

I currently have a very old-school tube DAC that I built. I was thinking of adding a modern solid-state DAC that plays high res, and switching back and forth between the two.  

You can do that, but SQ may be impaired. The same chip is dealing with both outputs, you may have more jitter with both active than a single one. For comparisons sake, both outputs will probably be affected equally, so A-B test still ok.

On the servers, the optical (Toslink) transmitter used for the digital output is unswitched and therefore it is always electrically active, providing a consistent electrical load upon the digital output–so it shouldn't matter whether it is connected or not (it generates light nonetheless).

You might notice, on the other hand, that the presence of a coaxial electrical connection upon the coaxial (BNC) output (as used on the UnitiServe) could affect the performance of the Toslink (optical) output in a minor way–it's worth auditioning all four ways (coax solo, coax both, optical both, optical solo) just for peace of mind.

Some systems, depending on ground plane or other noise factors, might benefit from the isolation that Toslink provides.  Try it and see!

(Absolutely nothing to contribute to the topic here -- sorry --, but nice to see you posting again around here Dave.)

Thanks for the comments - going to try using both outputs, and see how it sounds.

Dave