This has filled me with fear!
Are you using the 7236 power tubes on the WA22 or similar that produce 2 watts ?
Well as I feared my WA22 drives the HE-6 with the high gain tubes, but just barely. I have it pegged and the volume is loud but still listen-able, so obviously there is no headroom with that combo. I hope they scale up with my 50wpc power amp like the protos did, as this is similar to the experience that I had with the loaners. Unfortunately I am in the same boat as HA and am without a pigtail adapter atm, but I am working on it.
One thing is clear so far, the HE-6 is not a good compliment to my HD800 out of the WA22. Their power requirements are too different, and with the WA22 amp even single-ended the HD800 wins as the HE-6 is under-driven. Also their sound signatures are quite similar when compared this way; the HD800 has better soundstage and bass texture/extension, while the HE-6 is exhibiting a bit of a lower-mid bulge but yes very smooth upper mids and treble. But between the two headphones there is not enough sonic contrast, like there would be between the HD800 and the LCD-2.
When my pigtail adapter materializes it should be a different story and I expect the HE-6 to re-take the lead. And yes, with a $350 power amp compared to a $1900 balanced Woo with upgraded tubes, based upon my experience with the protos in the loaner program. Also now I am planning a hopefully bad@ss iPad rig for the HE-6 with that Alesis speaker amp and a Devilsound v2 DAC cable that I just picked up on the cheap off of fleaBay.
The jury is obviously still out for me on the prodo HE-6, but I think that a couple of things may have been overblown in regards to the changes from the proto version. The prodos may be easier to drive than the protos were, but only very slightly. And the differences in sound are perhaps more apparent when they are less than optimally driven but that could be hopeful optimism on my part. I am looking forward to that same speaker amp upgrade magic that I experienced with the protos when I finally hook the prodos up to the Alesis.
Next up is comparing the HE-6 single-ended to the HE-5 out of the EF-5 amp, probably later tonight. I will also drag the HD800 up to that rig to be able to more fairly compare them to the HE-6, with both getting enough juice out of the same amp. The HE-6 is already compelling me to change a few things around, but I already knew that would happen.