I stumbled across this little portable amp in radioshack while I was on vacation and while I was in the store I did my absolute best to hate it about right until I got it out of the box. When I pulled it out of the box I realized it was the exact same size as my Sansa Clip Zip which I had retrieved from the car along with my grado sr80i that I genuinely believe sound fine without amplification. My buddy and I both did blind tests and were able to discern when the amp was present on songs that we were familiar with; we agreed that it marginally improved the soundstage of the headphone. Then I learned that it was 20 bucks, throw in military discount and I am sold for 17 big ones.
The Auvio ended up being rubberbanded to the sansa and I listened to it for a long time over the next week of vacation with the sr80i's and a modest collection of flac files these were my observations.
-This thing is powerful you could easily damage your ears at even half volume (output power 150mW 16 ohm loaded)
-The equalizer has four settings, I kept it on flat almost the whole time except when I was listening to my some raps where the grados were lacking. The settings are; Flat, EQ1 +5dB bass and treble, EQ2 bass increase 10dB, EQ3 Bass +10dB and Treble +5dB
-battery life seems fine
When I got home I hopped on head fi expecting to read everything that I thought about the thing was wrong and I was stupid but there was nothing so I decided to get serious and get a user name and write a review. This time I plugged it up to my JDS labs Odac and selected a list of songs that I remembered hit the spot coming through HD650s powered by my Marantz AV receiver... (I know, I know)
I started first by using the grados as I was familiar with them, the high level distortion was much more noticeable out of the Odac but was nonexistent to my ear at any reasonable listening volume.
I plugged up the HD650s which the Auvio powered confidently and I turned it up to ear-shattering levels momentarily looking for that distortion which never showed up. I referred to the manual and the Auvio says its appropriate for headphones between 16 and 300 ohms impedance. It powered the 650s well but side by side with my Marantz unit I did find the Auvio to be slightly fatiguing with a slightly smaller soundstage as I studied the sound. I am impressed by its ability to power them compared to a computer headphone jack or the sansa alone but I most likely wont be plugging the 650s into this thing again since they never leave the house.
Its safe to say that this little amp will happily stay with my portable rig though, I wish I had another portable amp to compare it too.
I have some pictures I wanted to attach too but since Im new I dont have permissions, will patch em in if/when I can.