it actually sounds really nice, had a morning test in the office whilst working away,. With the hd650s, its hard to fault it - really nice presentation. definately more classically tubey (coloured!!) that the solid state infused parafeed designs, but for someone wanting to there the 'valve sound', its a nice amp. With a good dose of NFB, it handles sensitve 32ohm planars ok, anything low imp and insensitive, forget it, it fails miserably.