Cobbled this together out of some interesting off-the-shelf components:
- USB Audio Bluetooth dongle ($5)
- 30Wx2 Audio Module Class D Digital Power Amplifier Board $5
- LM7805 voltage regulator with some caps (I used two 0.1 uF caps)
- 10k potentiometer
Assembled this on a 1-1/2" x 2-1/2" PC board. Grounded the components to the board with solder braid. Used an old speaker from a boombox that I garbage picked. Solder blobs left on the board for effect. I'll reduce the length of all the wires and then probably mount this in a wooden cigar box as an enclosure.