In reviewing many product pages, I found a single ~$70 HDMI switch w/ RCA audio out that *claimed* to do what I wanted but was from a no-name brand on a no-name website; this was sketchy enough ...

Been reading up on things here about dos and nots of RCA cables ... a decent output. I'm just lazy and don't want to have to plug and unplug the cables every time I switch the audio over.

With Arduino library ... appealing to the synth / audio geeks among us. And now, with just the addition of a highfalutin LED and some software, the Teensy can output digital audio over optical ...