I just got one of these bad boys yesterday. I have found that I have a lot of times when I need to practice, and don't have an amp as an option, cause I am on the road, on a lunch break at work, etc. This bad boy runs with either an AC/Adapter or two 9V batteries (supposedly 50 hours of life on a set). I noticed no difference in sound or performance between battery and AC performance. Tried it out last night when I got home, just to see how it all worked. First impression. This thing is very nicely built. It looks and feels very solid. The headphones that come with aren't stellar, but they are good enough, and don't seem to distort at all with any amount of bass through this box. I will say that I only play 4 string, though, so I don't know they would hold up to a low B. My bass plugged straight in, sounded like itself. That was my first big hope, and desire. The sound is pretty transparent -it felt to me like a soundcheck in a studio where I was plugged straight into the board. There is no extra noise that isn't coming from my on board electronics - none in the earphones and none from the PHA-1. The dynamic response was pretty good all around. I could here a whole lot of the little string noises and subte nuances going on. Sloppiness in my playing stands out on this thing. That's for sure. The line in feature is very cool. You can control the balance/mix of your instrument vs. a metronome or stereo input or whatever else. I have already used it very happily with a metronome and my MP3 player. Overall, I am very happy with this new little toy of mine. I intend to have it with me pretty much at all times. I can now and shed or groove or whatever, in the back of my truck, at my gf's house, or in my own place at 2 in the morning without angering anyone. I can't promise my playing is gonna get any better, but this thing will definitely help me to spend a lot more time practicing. Sometime soon, I will check it out during a rehearsal or gig as a pre. If nothing else it should at least be an adequate preamp backup for my normal rig.