Originally Posted by ghostmusic
Hmm, I dunno... I kinda have the opposite reaction, that with a quality tube amp, the HD800 might have a really deep soundstage, more holographic imaging. But I do get where you're coming from... I've definitely heard crappier tube headphone amps than SS amps, but when glass is done right, nothing else compares. I, for one, look forward to trying my Leben CS600 with it first. Or, as I said, the OTL/SET config of WA2 would complement the Senns well... or the WA5s!
I know what good tubes can do: I prefer the Earmax Pro for my HD650.
Generally tubes are better with high impedance phones (like the 300 ohm from HDS650), but I think it also depends on what causes the high impedance and need for voltage. I think the HD650 has (physically) relatively heavy and stiff drivers that need a lot of voltage to put in motion and to control them. It also explains their extremely (compared to other phones) positive reaction to balanced driving.
I think that the HD800 (because of this ring construction) has a much "looser" diaphragm. The initial impressions that describe them as fast and spacious also support this. It will move easier and more and thus will need relatively more (fast supply of) current than the HD650 do to properly control them.
Just my speculations.