HD800s came in. Using 2 well respected, for the HD800s, headphone amps from 2 very well repsected headphone amp companies, they performed well. A bit coarse in the highs, and a bit prominent up there, and a little lean through lower mids and upper bass, but very clear, very transparent, and about what I would expect from reading hundreds of comments about the 800s. Problem is, not as easy to listen to as most of my speakers. Granted, speakers, amps, preamps, all that upstream stuff totals several hundred thousand dollars in my systems, so it hardly seems fair to compare when I'm substituting a few thousand dollars of headphone electronics for over $100k of preamp and amp.
So the itch remained to try my normal preamps (the headphone amps do not have an input avoiding the preamp, so I cannot avoid the headphone pre and use my great preamps) and my favorite speaker amp. Interestingly, many folks (the majority) said headphone amps are better, speaker amps have poor signal to noise ratios that headphones would uncover, not enough detail. I decided to try the idea I talked about earlier of loading the output of the amp at 10 ohms (could not find a high quality 8 ohm non-inductive wire wound resistor) and a dropping resistor after that and before the phones, starting with 100 ohms.
Well, the sound is phenomenal. A huge difference in width (not my most important thing), a major increase in refinement (really I'm saying major decrease in grain/distortion), beautiful sweet sweet, delicate highs with tremendous extension, deeper bass (the HD800s go amazingly low in the bass if the amp is stiff enough). The transparency is really amazing. I wondered if a bunch of parallelled tubes (8 per side) would be a bit crude or coarse at extremely low power levels, but it is the opposite. I will be trying several other speaker amps and will report. Certainly, information I received about speaker amps being too noisy, volume control will be at the bottom, headphone amps being much more detailed were simply not true. At least not universally true.
What amazes me is the sparse information about running headphones this way. To use dual mono amps I will need to make a "balanced" headphone cable as it would not be a good idea to have the speaker ground terminals of 2 different chassis tied togethere. Hope this information answers some questions for folks. I also would like to caution folks to not try this unless you understand exactly what you are doing, and have confirmed that the grounds of your left and right output lugs on the amp are connected. Further, no bridged amps, no dual mono amps. Dual mono amps should not be used unless the headpone wiring is balanced (different grounds on L and R channels, NO headpone plugs!)
Edited by Operakid - 2/22/13 at 4:25pm