Hi ngkou,
It's impossible for me to put a percentage figure to how closely your gear comes to the pinnacle of HD800 performance - in part because I've never heard your chain, but I seriously doubt that my best chain comes close to making the most of the HD800. It seems to scale endlessly. The HD800 is seldom the limiting factor - not even for bass performance. You just have to give it what it wants.
Read this recent post by
@johnjen
A couple of years ago, I was at a meet in the Dallas area where
@jazzerdave had brought his Cavalli Liquid Glass > HD800 rig.
I've never heard any headphone system that was more to my liking than what I heard that day. At that same meet, I had spent several minutes listening to a Stax system and a Sennheiser Orpheus HE-90 driven by a Headamp Blue Hawaii. Jazzerdave's HD800 rig was far better, in my opinion - for a lot less money - even though it's way more money than I would ever spend. It was astonishingly good. Jazzerdave was using a Windows 7 laptop with XMOS-based USB-to-SPDIF converter providing Coaxial input to a Peachtree DAC and from there into the Cavalli Liquid Glass amp with who knows what tubes mounted, balanced out to an unmodded HD800. It was stunningly transparent, neutral, and natural sounding - with nothing but blackness around every last nano-volt of micro-detail, with bass that absolutely growled when the signal called for it - texture and control beyond belief. The HD800 was very happy on his rig.
I would say it's wishful thinking for me to claim that I am more than 70% of the way to what Jazzerdave's system can do, but I'm not about to spend something like $5000 on such a rig and get caught up in buying dozens of tubes to find the setup that sounds the best. And it's possible that someone out there has an HD800 rig I would like better than Jazzerdave's.
You and I are "middle-class" audiophiles, my friend - and that's perfectly OK. I have other hobbies in which to spend my money - hobbies in which I am far more creative and productive and find much more rewarding than passively listening to music in my recliner.
To answer your question, an amp can be Class A yet still use lots of negative feedback to tame the distortion caused by multiple gain stages. The problem with such designs is that use of negative feedback actually creates new distortion artifacts down near the noise floor at very low energy levels - not easily detected by low-resolving headphones (or speakers), but easily detected by the HD800. This is why (in part) the very powerful but high-feedback multiple-gain-stage amp of the Oppo HA-1 measures well for distortion and noise, but sounds bad with the HD800, while sounding absolutely wonderful with planars and just about every other headphone - because they're not capable of delivering those micro-details in the first place.
Some people think the HD800 has a problem that needs to be fixed. Other than a 6 kHz spike that has been addressed by Sennheiser's new "
HD 800 S", I am in the camp that says the fatiguing, brittle edginess or harshness that so many people hear in the HD800 treble (at frequencies much higher than 6 kHz) is NOT a problem with the HD800 - it's a problem with the signal coming into the HD800 - a problem that cannot be detected by less resolving headphones. The Oppo HA-1 has this problem, as does every other amp that uses a lot of negative feedback to remove the distortion caused by multiple gain stages. Zero-feedback amps, like the Metrum Aurix or the $480
Audio-GD C-2, may have other problems, but they do not suffer the degradation of every audio trait that benefits from well-resolved, undistorted, low-energy signals that reside close-to-the-noise-floor. When the micro-details get obliterated (which is typically the fault of the headphones, not just the amp or DAC) you suffer losses of soundstage, imaging, ambiance / air, and even a naturalness of timbre - in vocals and acoustic instruments. Everything from violins to drums and cymbals can sound less realistic when these low-energy signals are corrupted by use of negative feedback.
I am not an electrical engineer, but from what I've read, the trick in designing an amp that uses no or very little negative feedback is to add power without creating distortion in the higher energy signals. True, single-ended designs manage to do this - as with the HA-200. And I can attest that the HD800 loves the HA-200 - as several other people have found. It would be a more popular amp if it wasn't so affordable and frankly, boring in appearance. Joe Consumer wants gear that looks good and he automatically assumes that if it costs more, it must be better. As I wrote before, the soundstage and dynamics of the HA-200 is better than that of the much more expensive Metrum Aurix, but just a little bit softer in terms of resolution - which I attribute (at least in part) to the HA-200 being low-feedback instead of zero-feedback. If you want to hear every last morsel of information a DAC is extracting from a given recording, good or bad, use the HD800 with a zero-feedback amp. (I'm not saying all zero-feedback amps guarantee this performance - I'm just saying that you can't get there with high-feedback designs.)
But I think you should just enjoy what you have for a while. The longer you spend listening at any given level, the more experienced your ears will become at discerning the nuances that distinguish good from really good audio - which is actually a curse, not a blessing. Adaptive hedonism will continue to make boring that which was once exciting. You will eventually get the itch to upgrade, then you'll buy something and just because it sounds different, you will find it a welcome change, but switching back to the previous component after a few weeks might reveal what you've lost with that upgrade. My advice is to move s-l-o-w-l-y or even, not at all. At some point, you'll realize you are going in circles - as I have been lately, bumping my head against my self-imposed money ceiling. Enjoy the music!
Mike
