Hey PB,
Thanks for the prompt reply.
The USB cable is, I think, roughly 10 feet long; it will run across the room from the PC just to try out the DAC. I think it came with a printer or something like that, so I doubt it's any great shakes as an interconnect (though, who knows - might be the sleeper tweak of the century).
The selector switch is a good idea; I'll do that.
I'm presuming that with no source connected, a display readout of 8.8.8 (kind of all segments lit) is normal.
thanks,
David