The 6sn7 swap was for me the best step to" trying to find the best tubes for the dac". I came from stock 6h6 (which are the best bang for buck) to EH 6h30pi gold pin which are way to clear for me and after a while found a match with the 12bh7 full music tubes. The FM where really my taste, quite warmish and laid-back. Then I discussed with Garry to try the 6sn7, for me the 6sn7 is the best pre tube there is al ever made(use it also in my amplifier) and with the mk3 deluxe version motherboard upgrade it was very capable with the new gain and I tried those. I use a custom made adapter from the brand eizz and all I can say is that if you like the warmish side of sound. Like typical sun audio, horn speakers, 2a3 sound, you better have to test these out! I also have Sylvania vt231 and the Jan's rca vt231 nos but there not a match in the dac. Quite dull, nothing special.. But a friend of mine was giving me a recommendation about the nanking 6h8c from the 58 year and that 1 is still the best tube for in the dac. But because it's shortish stock and price is getting worse (read higher) is saw linlai came with the elite version of 6sn7. So now I'm testing this to see if it can beat this Nanking or at least close. And all in all I can say linlai does it again and it gives such a good natural quality to the music, very realistic. But again I don't like the ES Sabre, EH psvane dynamic sound where every "sshh, highhats or harsh and every detail is noticeable.. Want to put music on and listen for hours and hours without getting tired of it. It's all comes to your personal taste.. Cheers