Thank you for your update. Indeed I am thinking of building this amp for my Susvara. I had built a Beta 22 (full balanced version) and it drives my Utopia beautifully. The sound is very neutral with great dynamics. Yet with the Susvara, it sounds lame with a lack of impact. System matching is therefore really important.
Talking of DIY, I built a 300B based preamp with a headphone output a few years ago produced by Transcendent Sound (
https://www.transcendentsound.com). The model is called The Masterpiece. It is priced reasonably and they have a great support forum as well. Bruce the owner is a very nice guy.
I bought this kit with the intention of using it as a preamp buy much to my surprise, the headphone output works so well with the Utopia.....it's really better than any h/p amp that I have had the opportunity to come across (including expensive amps from Woo Audio, Eddie Current and definitely the Beta 22). One really needs to listen to this combination to appreciate why OTL amps have so many die-hard followers.
This is a challenging build....no PCB, everything is hard wired. One word of warning though, this is NOT a universal h/p amp. The Utopia goes so well with this amp because of it high efficiency and the happen-to-be-so-right impedance. It works well enough with my Ether but not at all with my HD800 (high impedance). Forget about the Susvara! If ever I have only one choice, I would happily live the Utopia/ Masterpiece combination.
As a final thought, for $2.5k, I believe ANK should have come up with a more 'complete' product so builders shouldn't have to encounter 'issues' during the build process.