im a noob in audiophile stuffs.. so please take my words with a pinch of salt..
anyway, im pairing this amp with my Senn HD518 and Audio-Technica AD500. With the Senn, this amp brings out fuller mids, and helps to balance out the dark sound signature of the Senn. Great for jazz and classics. Overall the sound felt 'smoother', dunno how to describe properly..
With the Audio-Technica, which has great mids and clarity but weak bass without an amp, this amp gives it a slightly more solid bass. Not punchy, but just nice so that u can feel the bass without ending up with a headache.
I can pretty much say that the amp has a 'warm' sound signature. Gives u that warm fuzzy feeling when listening to music. Great if u just wanna relax and enjoy some slow songs.
Only problem is microphonics, which i guess is usually present with most tube amps. Once the amp warms up properly, the microphonics will disappear.