“This project was born out of constellation of things and desires :) I’ve always wanted to make up a CMOY amplifier, just because I think it is a cool project and I always wanted to see if the headphones amplifier makes sense. I did buy my components, but never got to actually making it. Next, while looking through my stuff recently, I’ve came across these 16340 cells that I bought for some reason. And finally, being a long time user of PCB sensors (excellent btw), both in the academy and in the industry, I wondered if we can find a “better” use for their sensor boxes other than…well.. holding sensors :) It all boiled up to the point when I decided to fit a CMOY amplifier inside one of these boxes. Since we are in the modern age, of course it will be powered from rechargeable lithium battery which can be easily charged and used for charging phones and stuff. And being in the modern age, why not fit an additional Bluetooth speaker to the device? The merit for this is as follows: the main functionality is to be a headphone amplifier (it is worth it by the way). Then, every once in a while you will need the bluetooth speaker, so just flip the switch and use it. And along the way you will want to charge an occasional phone. This device will give the answers for all three. So, here it goes, I hope you will enjoy this instructable.”