Let's hear it for the Pi #
It has been a month or more of trials, setbacks, false starts and dead ends. Apparently, if doing this sort of DIY RV home automation and media center thing was easy, more people would have done it already.
And getting usable audio in the trailer was definitely one of the big hurdles, even before I ruined the Pi SD card and had to start over.
It's hard to believe it's been almost two months since I got the touchscreen in. Like I said, there have been a lot of false starts in between.
Picking up the thread again, after the touchscreen was fully installed and framed in I had a wonderful touchscreen and a Pi running Plex to show movies, and a new problem: I couldn't hear them. The meager speakers in the monitor were mostly covered by the frame around it, and it didn't matter because the Pi couldn't really push enough volume anyway.
Figuring I didn't need audiophile quality just to watch a movie at bedtime or if it's raining, but I did want to put a premium on low-weight, low-cost, low-power solutions, I ordered a Kinter MA170 amp from eBay and some nice little marine speakders.
I committed to doing it and cut holes for the speaker in the new closet door I had just made a couple of months earlier. Wired it all up and... it sounded horrible. Just horrible. A whiney, popping mess. All noise, no audio to speak of.
So I spent money on noise suppressor clips that helped, but not much.
And I bought a HifiBerry which, honestly, seems to solve a different problem. If I'd bought the version with a built-in amp it might have been just the ticket, but I'm unlikely to find out now. This was also a particularly painful dead-end because I spent a long time unwinding the audio settings it needed changed, and I'm still not sure I've got that completely sorted out.
Then I bought a noise isolator which also helped, but not enough.
I mucked around with the power feed, with all sorts of settings (both in hardware and with software) and generally tried everything until finally I figured that everything was playing nicely, albeit with low volume, except the amp. So I broke down and bought another amp.
And this turned out to be a nice little amp for the purpose. The noise problem was gone immediately, it's plenty loud for the trailer and the sound quality is pretty good, even through the diminutive speakers. It turns out the original Kintner amp was just trash, which is why I won't link to it. The new amp works great, though. I'm happy.