Pros: driving very well some headphones.
Cons: wont match to many headphones.
i have checked this amp with 4 headphones: AKG Q701,sony MA900,soundmagic HP100, Hier Audio 4.AI.
from this 4 headphones only the akg q701 sounded good with the amp1...
and that is a surprising thing becuse i have cheked the q701 with alout of amps (like the ibasso pb1, pimeta v1, little dot mkIII, AMB M3)
and non of theme really drives the q701 good, In fact they made the q701 sounds flat\dry\thin mids\too big soundstage\not natural
and becuse of that many poeple say that the Q701 sounds bad...
but at the first time i heard amp that doing to the q701 somthing that i didnt heard before,
it made the q701 sound like it should be, many poeple say that the only upgrade from q701 is HD800 and now i can say that i agree with theme :P
so the only thing that bad in this amp is that this amp wont match to many headphones
but whene this amp matches to ather headphones it makes theme sound really good
so in my opinion, if you have Q701 or K701\2 and you are looking for an amp
i think that the amp1 is the best choise you have in this price range.
Updating: heard the HD600 and the HD650 with the amp1... and to my opinion, the amp1 driving really good the HD600\650 (not only for amps in this price range)
by the way
i have the upgraded amp1: http://rwaudio.com/store/#!/~/product/category=173875&id=416522