the O2 made a big difference with my DT770 Pro 80's compared to coming directly from the Titanium HD headphone out. the bass tightened up significantly. i attribute this to the change in damping factor, but i'm pretty new to the subject so take that for what it's worth. if you find the bass to be a little uncontrolled with your DT770's the O2 is the way to go. other amps may achieve the same result, just my personal experience with the O2.