I want to commend
@Noendgamehere for having the courage to challenge the ASR orthodoxy. It's pointless to take such a hard-line stance against the utility of subjective evaluation when the sole end goal of hi-fi design is to deliver a pleasing subjective experience to the listener. The only thing that matters is how it sounds. If ASR wants to do something serious about fraud and misinformation, I suggest you all turn your attention to politics.
To answer the original question, the Mjolnir amplifier seems to be competently built. The hand soldering is a little sloppy by my OCD standards, but looks to be perfectly adequate. I looked up the referenced Kevin Gilmore circuits and they appear to be well thought-out. There seems to be a little controversy WRT the relationship between Gilmore and Mjolnir, but I can't really comment on that.
Whether or not it's worth the asking price is tough to answer. I would be hard-pressed to build that amp and make a profit selling it commercially for much less than two grand. Measurements would probably reveal poorer performance than the latest toys from Guandgong Province, but Mjolnir doesn't have the benefit of the economies of scale, cheap labor, and government subsidies (direct or indirect) enjoyed by Chinese manufacturers. The amplifier probably performs well enough to be "audibly transparent," whatever that means. Or perhaps it adds a little bit of "flavor" that some listeners might prefer. Personally, I think it's funny when people's heads explode at the idea of deliberately designing circuits to add some coloration to enhance the sound. It doesn't hurt anyone as long as no one lies about what they're doing.
If the threshold of audibility is 'X' and all competently-designed amplifiers meet or exceed that standard, then it's pointless and self-deceptive to rank these amplifiers on a scale of fitness for their intended purpose, which is to play music pleasingly. Nonetheless, people routinely go nuts over the latest record-breaking performance results, even lament having purchased last month's champion, all the while acknowledging that "it all sounds the same." IMHO, this is a glaring logical contradiction in the philosophy of this site.
From time to time, I see people making similar points here. Some of the arguments are pretty astute, IMHO, and I get a laugh out of the logical contortions that are offered in reply. People should be honest that, as
@JohnYang1997 himself said, the problem of amplifier design was solved a long time ago. The push for ever-lower noise and distortion is an interesting exercise in design ingenuity, but has no utility to the end user. It distracts from more important and useful things, like customer service, build quality, reliability, and, you know, supporting domestic manufacturers who have a hard enough time competing on an unfair playing field.
This site would be much, much better if it incorporated some kind of controlled listening evaluation, and offered actual in-depth analysis of circuit design instead of just posting Audio Precision plots and pictures of broken panther figurines. But it's not my site, and who am I to complain? I design and build my own amplifiers, and get several orders of magnitude more useful guidance from diyaudio.com.
I say, good for Mjolnir for building a unique, hand-crafted product that's different and interesting. Nobody needs hi-fi. If you have some expendable income and find the product appealing and satisfying, then go ahead and buy it. Otherwise, spend $150, be a lemming, and buy something from Topping. Or just listen with the "free" dongle that came with your iPhone.
I admire John Yang's work. Two years ago, he was a college student. I bought an A30 Pro recently, and honestly can't say I prefer it to my own DIY HPA, which has never been tested with an audio analyzer.
