You are better off hooking both DAC's up to separate USB cables, and use a preamp to switch back and forth. :)
Erik, thank you for replying.
My concern was(is) that simply splitting the streamer's USB output
would degrade the signal....perhaps even if one of the two recipient
DAC's was turned off. I currently use my pre-amp to switch between
the output of a universal player, sourced by its internal DAC, and
the 'throughput' of that player, to an external DAC. My object is
to add a second external DAC, and have the option of directing streamed signals to either external DAC, bypassing the universal player. The idea of employing 'at will' two external DAC's may not be that crazy given the potential desirability of choosing/using certain chip styles....Burr Brown vs. Sabre, for instance...in order to optimize playback of certain music sources....for instance, piano vs. violin.
Again, further ideas would be appreciated.
I think you are overthinking the entire thing. An isolator like an iFi may be a good thing though.
I also think you are using equipment to act as tone controls in the most expensive and difficult way imaginable.
Better to get an EQ before your DAC like the miniDSP nano. Some of the miniDSP models have network/phone access so you can switch profiles back and forth.