Thanks for reading it!
I tried my best when it came to volume matching as I know from a long way back that this is the most important thing to ensure when testing different amps. First i used the hd800 for an hour, then the d7k for 45 mins (not both interchangeably). When testing two amplifiers using a headphone, the first 4/5 times I switch between amps I don't compare their sound - I only try to match volume. Using a few tracks I'll find where they sound just beneath what I consider to be loud and leave it there.
When you do your comparison, you forgot to mention what output jack you are using from the amp. I am pretty sure that Solo Ultra-Linear is single ended, and if you do not mod your phone, they should all be single ended too. My guess is that you are doing an single ended output comparison across these 2 amps.
Well, for what I learned from HDVD800, the single ended output is good, but not as good as other top tire single ended amps (e.g. my rpx-35 or V200). The juicy part is the balance output. I wish you have some balance phones to do the comparison cause I am very interested in such reviews~~~~ Always wanna know how other phone in balance configuration sounds on HDVD800 compare to other SE amps~~~