OP, is it possible that your O2 is simply defective?
Edit: I just tested your "no amp needed" conjecture using my laptop, K340 (400 ohms), and the O2. Although I can get sufficient volume straight from my laptop, the sound is markedly different and better with the O2.
Also, sorry if this sounds like a "you forgot Poland" moment, but I haven't been able to confirm that the LG phones have Wolfson DACs.
Edited by Claritas - 3/2/14 at 3:04am