First things first, I think I may have wasted a bunch of other people's time on this and for that I apologize. I believe I have it all sorted, and I'm going to post the results in hopes that it saves someone else some time.
One of the unique aspects of my configuration is that I am using my living room TV as both a TV and as a monitor. I have HDMI from both the computer and the Comcast box. I take the audio from the computer SPDIF digital into the earlier mentioned Adcom DC 700, a DAC I specifically use because of its support of HDCD. Up until the installation of JRiver, all sound from the computer (including Youtube, Netflix, etc) came through the DAC and hence the amp and stereo speakers, and all sound from the Comcast came through the second HDMI through the TV speakers. Which worked fine because I have a home theater in another room which if I want to watch movies, etc., is where I go.
Once I set up JRiver to try and use the WASAPI output, things started getting weird. One thing I noticed once I hooked it up and specified that the WASAPI should be exclusively controlled by JRiver, suddenly HDMI started being used for stuff not being played through JRiver, which is to say the above media streams. Wow, somehow by accident I got that problem resolved. But the dropouts were driving me nuts, and it seemed to be getting worse. Finally, at the end of my rope, I decided as a last resort to read the instructions on setup again, and specifically the DAC setup section. And that's where I found a very important deviation from what I had done. I quote:
Media Center Windows 19
Audio Device
If your device has it's own driver installed, select it from the list. Otherwise the best option will normally be "High Definition Audio Device [WASAPI]". Find more information at Audio Output Modes.
Device settings
Open device for exclusive access: Checked
Disable event style: Unchecked (may need to enable this on some older devices if you have problems)
Maximize device volume during playback: Unchecked
And that's what I had screwed up, I had checked the Maximize device volume because that's what I had to do before to ensure that I was getting the full digital signal to the DAC. Once I unchecked that, everything started working as designed and imagined, and through four hours of play I've not had a single drop.
RTFM, as they say.
Anyway, I think I'm all sorted. I do note that in this configuration the playback indicates it's going out 32 bit, not 24, but hey, it's working.
I hope this helps, and I greatly appreciate the effort put in by people responding to my posts above and feel free to call me an idiot. My wife does.
