This mini-amp is the champ. Seriously. Not because of it's sound quality (which isn't bad for what you get, but also not great), but because of it's build quality. This miniamp expects an inverted barrel jack connector (voltage on outer sleeve rather than ground), and it does say it on the side, though it's not easily apparent (part of the molded plastic so it has to catch the light correctly to see it). Well, I didn't know that, plugged a standard barrel jack A/C adapter in, and got the wonderful magic smoke. I thought it was done, but when I reversed the polarity, the amp STILL WORKED. Amazing. It only blew up one diode (probably responsible for protecting the 9v from being charged on A/C power). Line out doesn't seem to work, but I did smoke mine, so it might have before then. Oh well, still impressive for what you pay.