AKG K712, AKG K271 mk2, Beyerdynamic DT990 PRO, Superlux HD681 with Burson Play

The play is my first unit from Burson. I choose V6 Classic. As far as I can tell after 2 weeks of use it plays wonderfully. It sounds slightly better than AIM SC808(2x OPA2227+ LM4562 RCA) + O2 AMP(2xLME49990 in gain stage) combo on my phones. When it comes to power capabilities it's much more superior. Looks great, the display, volume knob - even if it lacks precision sometimes. I don't use mic input. The major problem is even with high Impedance Headphones like 250 ohm DT990s, the background noise exists, no matter what volume I set (AIM808 and O2 is completely black). Noise gets louder after 30-60 minutes of use when unit gets warmer, Burson Play runs pretty hot, that's pure class A :). Wall wart included is poor quality, unfortunately. Maybe that hissing background noise disappears after burn-in time...