Today Plexamp informed me that it would update itself next time it started, so I restarted it to let that happen. Shortly afterward, Windows told me I needed to reboot to finish installing (its) updates, so I did that, too. When my system was back up, I started Plexamp and it worked well...for a while. Then I started hearing "popping" sounds in the music playback. Thinking it was just a bad source file, I tried the next track, and the next, but they all were doing it. I tried changing to a different playlist and after a few songs, I started hearing the popping again.
I thought there may be a problem with my Plex server's internet connection, so I brought up https://app.plex.tv/desktop and connected to my server to play the playlist that had just been popping in Plexamp and, to my surprise, it played flawlessly for the past two hours (when I stopped it.)
I think I'll wait for Plexamp to mature a bit before I try it again.