One day, I had theese old Thompson bookshelf speakers just laying around, and I had no way to play them, as I don't posses any good amplifier, that would suit my needs. I also wanted this project to be portable, to be able to play music wherever I go.
Step 1: Get All the Parts Needed
Theese are the parts I've used. Some, like toggle switch, I've got from local seller, but most are available on eBay, so I provided links to all of them.
$5 TA2024 audio amplifier board - http://goo.gl/ct122M
(optional) $3 Bluetooth Audio Reciever - http://goo.gl/CgS4TZ
$1 3,5mm cable - http://goo.gl/KJve1y
$1 3,5mm block - http://goo.gl/nRC9Xo
$1,5 Perf board - http://goo.gl/wqaK5Y
$4 Box - http://goo.gl/DwPpb3
$1 Thermal Compound - http://goo.gl/BLFlHH
$2 Audio Connectors - http://goo.gl/QmMkyY
$2 MicroUSB Boost Converter - http://goo.gl/ZjSKOO
$1 Main Switch - http://goo.gl/VF8wgl
The prices are approximate. I've got most of small components locally, for just a fraction of their ebay price, as no shipping is requiered. Overall, this is build under $15.
Step 2: Assemble Everything Like in the Video
Its very easy. As the board contains most of necessary electronics, we're only requiered to add power and extend the terminals and audio input. Before you put inside the boost converter, make sure to power it up and adjust the voltage using the potentiometer and voltmeter to check that its output is close to 12 volts. Then all you need to do is to make the enclosure. I had only drill and knife to use, but with Dremel it could have been so much easier.
Enjoy your new, budget-friendly DIY amplifier!