This is a small audio amp made for small portables. The circuit board is 21 mm X 24 mm. I got them from OSHpark and hand-soldered all the components. This is the ideal amp for me since I can never find a good, low-wattage amp to buy for my projects. Technical features: - 2W stereo speaker output - 150 mW stereo headphone output - 5v to 3.3v power input - 32-step digital volume control using up and down buttons One notable feature is that the headphone output is completely separate from the speaker output, so this amp can be used with small headphone jacks, like those found in smartphones. The headphone jack just needs to have one switch for sensing, as most of them do.