[Boolean90] needed an amplifier for a subwoofer, and had a lot of parts sitting around in a scrap bin. His project, a Class D sub amp made out of scrap, is a great example of what you can build wit… ...

They’re so simple, you can buy a class D amp chip for $3, but [George] thought that would be too easy. Instead, he built his own with an ATTiny and an H-bridge motor driver.