Lovely product, using it for my HD6XX and it's as advertised (by the community), delightful sound signature and much more capable of unlocking my HD6XX's potential compared to my portable dac/amp (oppo ha-2se). My current setup is Samsung galaxy S9 -> usb C to micro USB cable -> oppo ha-2se (dac only mode) -> lineout via 3.5mm to RCA -> mCTH -> HD6XX. What a match made in heaven. I feel that the sound is fuller and richer compared to before, and I get a general sense of increased musicality as result. If anything I want to complain about, it is that HD6XX truly is lacking in bass a bit, but it is at no fault of the amp.
I actually deferred my plan to purchase a headphone upgrade (focal elex) simply because the upgrade will be relatively more marginal with my headphone's new found performance.
I'll update this review if I ever try to pair this amp with another headphone in the future.
Edit: I'm now a proud owner of Audeze LCD-X as well as Focal Clear. Here's my two cent on the pairing with mCTH:
LCD-X: Not my cup of tea. This headphone is basically somewhat dark and has extremely good soundstage, with mid sounding a little recessed. Its delightful when paired with my Schiit Jotenheim listening to accoustics and live recordings, the bass also feels very impactful with Jotenheim. However, when paired with mcth the bass becomes relatively less impressive and the already recessed mid becomes even "softer" and warmer, makes it feel like the singer is standing 20 feet away while all instruments are only 10 feet from you. The amazing soundstage and warm sound actually becomes a negative thing.
Focal Clear: Whoa! What a matching!!!! Focal clear by itself has relatively small soundstage and EXTREMELY crisp and clean sound with ridiculous clarity and humble amount of bass. It has a neutral and slightly bright sound signature in my opinion. Pairing with mcth is very delightful as it softens and warms up the sound signature a tad bit which makes the music sound extremely crisp and clear but sweet sounding. It can be extremely revealing of bad recording but if the recording was done well, it is simply superb. In short, it adds musicality just enough that it makes the headphone to hit the sweet spot for me. In contrast when I pair this headphone with Jotenheim, it becomes overly analytical and dry sounding, with relatively little musicality that made it slightly hard to focus on enjoying the music.
I hope this update will be helpful for some of you out there that's considering the above pairings. Cheers!