Will get back to you on that one - I did quickly swap them over and think what the heck do I have the HD800 for but then I had the same reaction with the HD600 vs the HD800 when I first got the HD800 - I need at least 10-20 minutes to re-calibrate between headphones if testing the headphones rather than the amp....The HD650 are immediately more euphoric sounding, fuller, slightly more recessed mid range, and swapping them quickly make both the HD600 and HD800 sound a little anaemic - need to establish whether the HD650 are similar to the Soundmagic HP200 in that I initially loved them but after protracted listening they were too fatiguing to listen to...gave me a headache but I am extremely sensitive to artificially hyped treble energy (which the HP200 had in spades).....don't think they will be somehow....Annoyingly the HD Series all have their big pluses so I may have to keep all three (which wasn't the plan)
A few months back, I had all three of the HDxxx you are referencing, having since sold the 600 and 650, but can say that I fully concur with your comments, here. Selling the HD600 was easier than selling the HD650, but I stuck to the "plan" as you call it, out of frugality and ascetic self-discipline - neither of which come easily for me.
I do miss the HD650 and it has to be
the headphone for which I've heard more people say, "I've bought the <headphone>, again." I told myself then and I continue to tell myself, even though it's not entirely true, that the HD650 comes too close to the LCD-2 rev.1 to own both of them, and I've never had a problem ranking the LCD-2 above the HD650, for my tastes.
As a four-year LCD-2 rev.1 listener, it has taken me quite a while to
adapt to the HD800 - and the emphasis here is on my making adjustments to
my expectations when donning the HD800, so that I can enjoy what it can do as no other headphone can. But yes, in comparison to the HD650 and the LCD-2 rev.1, the HD800 does sound "anemic" -
especially if you are comparing them on the same DAC and amp. And
that's where I've made concessions beyond simply adapting
my own expectations to
enable the HD800. I've accepted the fact that upstream gear that works well enough with other headphones, not holding them back in any way, more often than not, fails to serve the HD800 well at all.
At least with DACs, every move I have made to improve the "euphonics" of the HD800 - to bring it
in the direction of the LCD-2 - has ironically only made the LCD-2 sound better as well, raising the bar all the more for the HD800, instead of closing the gap toward the LCD-2. But that's not the case with amps. To sound its best, the LCD-2 has a requirement for much more power than the HD800 requires, but the LCD-2 is also much more forgiving of amps that have a slight grain or distortion. The HD800, on the other hand, has a seemingly endless ability to ferret out even the smallest imperfections, as it can with the distortions created near the noise floor by amps deploying lots of negative feedback. (Cees Ruijtenberg, Nelson Pass, Dan Cheever and Robert Harley, among others, are all smiling in agreement...)
My ears tell me that neither the HD600 nor the HD650 can discern these low level distortions that the HD800 readily detects in the grainless but high-feedback OPPO HA-1, nor can the HD600/HD650 discern the very slight grain presented by the CEntrance DACmini CX amp section - a grain that I never knew was there until I got the HD800, but this grain is bad enough to mask any distortion caused by use of negative feedback in the DACmini CX. With absolute conviction, I can therefore decree (too strong a word) that the HD600 and HD650 are not as transparent as the HD800, not by a long shot, but they are more transparent than the forgiving LCD-2 rev.1, with its lower resolution and shelved highs.
And thus, I contend that the HD600 and HD650 might lack the transparency required to fully appreciate the zero-feedback nature of the Aurix. In the same breath I have to say that the benefits of zero-feedback are very subtle compared to nearly every other trait that is typically discussed when comparing amps, so I would, of course, want the Aurix to deliver on all counts, but I want to emphasize that where the HD600 and HD6500 might not even be able to appreciate the lack of distortion near the noise floor gained by use of zero-feedback, the HD800 might actually require it. It was Cees Ruijtenberg who recommended I consider a zero-feedback amp to deal with the remaining (fatigue-inducing) brittleness I was hearing with the HD800, following the considerable improvements secured by using the NOS Octave MkII.
Readily admitting that I have very little experience with tube gear, I am nevertheless convinced that
you have to spend a lot of money to design an OTC tube amp that sounds as transparent as far less expensive solid state amps, but it takes something like the HD800 to detect the most subtle differences. OTL amps use a ton of negative feedback to contain their output impedance and distortion, and I'm sure that's why, in part, I couldn't stand the sound of the the Schiit Valhalla 2 with the HD800, returning it under the trial guarantee - it was far from transparent! But somehow, the OTL Valhalla 2 is a popular "solution" for the HD800. I can only conclude that people are so pleased with how the still-prevalent OTL distortion smooths out the brittle highs heard with the HD800 on otherwise transparent but high-feedback solid state amps, that they completely overlook the negative feedback hash that's being generated down near the noise floor - stealing away all of those little micro details, echos, and trailing decays that so help to define the recording space and the timbre of instruments and voices. OTL and euphonic are often used in the same sentance, and that's what people like about Valhalla 2 - that it adds body and fullness to the HD800 but, in my opinion, this comes at the expense of destroying what the HD800 can do better than any other headphone, except perhaps for Stax gear. They might as well just get themselves some cheap EQ software.
OTC amps, like the WA6SE, are zero- or at least, very low-feedback designs, but from having spent
only twenty minutes listening to the HD800 on a Cavalli Liquid Glass system - the best I've ever heard from the HD800 or any other headphone to date - I'm convinced that an OTC amp has to be designed like the Liquid Glass, with expensive, neutral-sounding transformers, matching the impedance of the headphones, and expensive power tubes doing the work of driving the headphones (again, neutrally) while small triodes are allowed to "sing" without feeling the stress of any load.
I've never heard the WA6SE, but I don't have any problem imagining that it can come close to a "properly rolled" Liquid Glass, so I'm hoping that you can critically distinguish any shortcomings the more affordable Aurix has, when comparing it to your WA6SE with the HD800 - which, again, I believe is the only headphone you have that can appreciate everything the Aurix offers.
Thanks!
Mike
