thanks to this old thread, i've took the plunged with the HA-01. been burning it in for the past month and used many different cans with it.
some of the cans tried were D2000, D1000, DT880, DT990, DT531, DT831, A900, A1000, CD900ST, HD600, K701, RS1.
i've not experienced any noise that was discussed early in this thread. maybe it's the new improved version, i don't know. right now at least, it's dead quiet.
sonicswise. DAMM! u guys were right on the dot about this being an amazing amp. the bass kick and speed is really excellent. it's got nice air and stage, and wonderful musical immediacy. and all of a sudden the stubborn K701 is singing effortlessly. it's especially enjoyable with the Denon D2000 with great midbass whack and the vocals were sweet with a slight forward feel. it makes the other cans come to live! not a laidback amp but a little aggressive.
are any of you still using this amp? has the noise gone away?