A few years ago my wife and I decided to get a pet. Somehow we decided to get a bird, eventually selecting a cockatiel. One of the things we've learned while raising our bird, Dusty, is how remarkably smart parrots can be, and how much attention and interaction they need to remain emotionally stable and happy. Realizing Dusty would probably appreciate some music when stuck in his cage during the day, I put together a little music player based on a Raspberry Pi and an audio amplifier.
I wanted to be sure the music player wouldn't hurt Dusty if he chewed on it, and also wanted to make sure it would be easy to clean, so I built it in an old card catalog box from a second-hand store. The hardware is my original Raspberry Pi Model B and a hand-soldered audio amplifier PCB. The software is Pi MusicBox and has proven to be quite reliable so far. The UI is web-based and the Pi connects to our network via wifi, so the only cable coming out of the box is the power cord.
The amplifier is a simple circuit based on the reference design included in the TDA1011 datasheet, with components scavanged from my parts box. This circuit was assembled on perfboard and powered directly from the 12 volt DC power supply feeding the music player. The Pi is powered by a 12v to 5v buck converter mounted inside the box.