Thought I’d add my impressions to the discussion. First and most important comment: all the tubes I’ve listened to sound good when they’ve had at least 20 hours of break-in. The difference from one to the other are relatively small and are a matter of personal preference as much as anything.
Second comment: the Russian NOS is the default tube Schiit supplies with the amp. The TS 6SN7 GTB is the alternate tube Schiit supplies. The NOS Tung Sol is a 1953 6SN7 GT. Pics of each included.
Third comment: My set-up is as follows: Spotify or Tidal > Schiit Modi 2U > Schiit Loki (set to bypass for comparison) > Schiit Lyr3 > MrSpeakers Aeon Flow Closed (AFC) or Hifiman HE-400i.
Fourth comment: I’ve got a 1952 Sylvania 2 hole bad boy on the way. Will add that when I get it.
Russian NOS: great neutral tonal balance. Fantastic high end- smooth, detailed, but not at all fatiguing and doesn’t feel rolled off. Mids are quite engrossing and incredibly detailed. Deep thick bass with no bloat or bloom. Soundstage is medium width with good placement of instruments. Very realistic rendering of voices and instruments. Seems to work much better with the the very balanced AFC than the 400i which sounds thinner and dryer.
NOS TS: Brighter at the top with a little grain. A little dry in presentation. Good percussion accompanying string plucks. Might work really well with dark phones. Could be fatiguing with bright phones but would probably work well with headphones which have a tendency towards bleeding bass into the mids. While Impact is bigger than russian NOS, quantity of bass feels less. Upper bass pulled back. Soundstage is outstanding- wide, deep and stable. Guitars sound awesome if not as tonally accurate as the NOS Russian. Needs more burn in time than the tubes Schiit furnishes for the top to soften up. I’ve only let it burn for about 24 hours total during which the highs have gone from too bright and a little harsh to softer and smoother. Still not to my taste- too dry.
EDIT: Somewhere around 70-80 hours this tube really blossomed. Tone has improved, soundstage has gotten better, detail is stunning and top end is smooth and sweet. Definitely not a bass head tube and still light on the lower minds, but the soundstage and detail make up for it.
New TS 6NS7 GTB: fantastic mids right from the start (15 minutes burn in). 10 hours later it’s even better. Perfect for voice and guitar. Lots of air.
The highs are clean and smooth. Great detail and resolution. Lows are meaty like a Prime steak. Upper bass is like a warm soft blanket on a cold night. Not as neutral sounding as the Russian NOS. More tubey with a very polished and smooth character. Basically a great big euphonic sound. Makes both my 400i and AFC sound gorgeous. I suspect it makes any headphone sound great as long as it can handle the upper bass without bloat. Holographic soundstage makes you feel like you’re standing in the audience. Dynamics are energetic but not overpowering on my phones.
The synergy between this tube and the 400i is impressive. It may not be as competent as the Lyr 3 + AFC but it’s close. The combo definitely works well and creates a great place to put your head.
To my ears it’s the best sounding tube so far for headphones which might otherwise sound a little dry. Definitely worth the additional money if you want to have a little more tubeness than the stock russian.
and going in the amp this morning. I will report back after some burn in.
