I've built a portable digital jukebox, incorporating the Raspberry Pi 3 B+, running Raspbian Stretch from a 32GB SD Card. I have attached a 128GB USB3.1 thumb drive as the device's main storage device.
Wifi access is via the Pi's own WiFi as is Bluetooth which runs a mini keyboard. That leaves two USB ports free. The only external cables are the Dell power supply (removable) and the RCA cable to the second speaker. I am building a portable power brick for it so I can play it on the go.
Voltage was an issue, so I incorporated a Buck Converter into the build which ensures a minimal voltage of 5.2 volts from the 19.5v 4.62a Dell laptop battery charger. The Pi 3B+ doesn't like voltages going below 5v, which is often the case with standard USB chargers, which may be rated 5v, but actually only have 4.95v available for the device.
Since I added the Buck Converter, I haven't had a single occurrence of under-voltage messages, or the dreaded yellow lightning bolt. I also added a heat sink to the Pi CPU, to assist in cooling it down as there is little air-flow in the box.
The Pi's audio output is connected to a TPA3116 D2 Dual Channel Digital Amplifier Board, to which I have attached a couple of speakers salvaged from an LG HiFi tower. The amplifier is also powered by the Dell laptop charger.
I have attached a 5 inch RPi HDMI touch screen monitor, set to portrait display.
The thumb drive contains around 10,000 MP3 files and a downloads folder, as there is not a lot of room on the SD card. I have downloaded the open source Clementine Music Player, which is now available for Raspberry Pi, which I can use to access hundreds of streaming radio stations all round the world.
All in all I'm happy with the Pi. I have stress tested the device, playing internet radio for 48 hours non-stop, whilst running a number of Linux-based CPU stress tests.
The photos shows the completed device. This is my first ever electronic project so it is a bit rough around the edges. The second speaker is removable to enable stereo sound separation. It has been painted with black 'hammer finish' spray paint and mesh covers for the 3 inch speakers.
Having now finished the project, it works well. It boots in 23.8 seconds. It has got plenty of oonce, in fact my crockery rattles when I crank up the volume.