Shootout of Nos 6sn7 tubes

@tksteingraber I have found that the National Union 6F8G round plates are very special tubes in my Supratek Syrah. I also have the NU 6SN7 round plates and the NU 6F8G sound better in every way. Also have Tung Sol VT-231 round plates (transparency kings), KenRad VT-231 staggered plates (bass kings), Sylvania T-plates, Baldwin flat plates, Sophia Electric, and Shuguang Treasure CV181-Z and the NU 6F8Gs are my “go to” tubes.

Keep in mind that the Supratek power supply’s rectifier tube paired with the output tubes has a significant influence on the sound (I like the Phillips 5R4G rectifier with NU 6F8G while the Mullard 5AR4/GZ34 Fat Base rectifier pairs better with the TS round plates IMO), so some mixing and matching of rectifiers is important.

Re: Raytheon 6F8G T-plates vs flat plates, the T-plates are much easier to find but the flat plates (scarce as hen’s teeth) are said by many to be significantly superior sonically.

@tksteingraber IME, the KenRad VT-231 and NU 6F8G can sound a little closed in (lacking air and sparkle on top) with the Mullard GZ34 rectifier in my system. If you find that to be the case after becoming acquainted with them in your system, try a more lively rectifier like the Phillips 5R4GYS.

@tksteingraber i was fortunate to buy two of the Phillips rectifiers back when they weren’t so pricey. Perhaps someone else on this thread can recommend another rectifier with similar sonics. For now, just see how you like the KR and NU with your Mullard GZ34…

I have not yet heard any other 6F8G tubes in my system. It is sometimes said that the other 6F8G’s (TS, Raytheon, etc) sound very similar to their 6SN7 counterparts with the NU being the exception, but I do not have first hand experience with the others.

I found this 6F8G thread informative: https://www.head-fi.org/threads/6sn7gt-6f8g-an-exploration-of-wwii-era-octal-tubes.890205/

Unfortunately, as always seems to be the case nowadays, the 6F8G models the author most prefers are unobtainium now (KR round plates and Raytheon dark glass flat plate).

I just broke down and ordered a pair of NIB/NOS Melz 1578s (the real ones $$$$). Will let you know what I think.

@tksteingraber Please let me know how you like the early Melz and the KR 6f8g.

@tksteingraber Glad to hear that you are enjoying the NU 6F8Gs. They have a very special blend of sonic attributes that I find impossible to beat.

The 1982 vintage NOS Melz 6n8s/1578 tubes I bought recently are sort of a mixed bag sonically. Extremely quiet (none of the crackling I read about) with the best bass slam/texture/definition I have heard (I prefer their bass to that of my KR Vt-231s) and unequaled imaging/soundstaging. Transparency is on par with my Tung Sol VT-231s. Upper treble is smooth and refined. Unfortunately, they are very forward in the upper mids, thus fatiguing after just a short session. They have improved in this area with additional play, but so far the upper-mid forwardness largely remains.

There is a ton of discussion on the Melz over on head-fi.org. Members Paladin79, bcowen, and JKDJedi seem to be the foremost experts on Melz. IIRC they feel that the Holy Grail Melz 6n8s is the early/mid 1950’s non-hole shiny black plates with the same micas and metal supports as the later 1578s. Good luck finding those at this point!

@1markr Thanks for the input on the Linlai Elites. I researched those a year or two ago and got lost in the endless back and forth forum chatter about which ones were the good ones (Horizontal or Vertical lettering, etc) and whom to buy from. Can you tell us exactly which ones you have (or better post a pic) and whom you bought them from?

@tksteingraber Thanks for the feedback on the 50’s Melz tubes. I find your observation regarding the constricted soundstage interesting. My 1982 1578 exemplars excel at soundstaging IMO. Perhaps a loss of some soundstaging is the price one pays to get the reputedly more balanced midrange of the 50s tubes?

Apparently it is not uncommon for the early Melz to have noise issues. IIRC there is a tutorial (on head-fi.org?) for resoldering the pins on Melz tubes that has been reported to yield positive results in many cases.

Regarding the upper-midrange prominence I was experiencing early on from the 1982 1578s, I ran the ISOTEK break-in/conditioning track several times and it seems to have further reduced this. These tubes are sounding very good now, but I still perceive that, despite the strengths you denote in your post above, they lack the musicality and emotional engagement of the NU 6f8g’s or the TungSol VT-231s. More time will tell…

I am interested in hearing your feedback on the Linlai Elite.

@tksteingraber Thanks for the thorough description of your listening impressions of the Linlai E-6SN7 tubes. Sounds like a good tube overall yet probably not one I want to add to my stable based on the weaknesses you noted.

The 1982 Melz 1578s have settled in very nicely as they accumulate more hours. I definitely place them in my top five. Still a touch forward in the upper mids but no longer objectionable. Their superb soundstage and bass continue to impress and, despite their reputation, one of the quietest tubes I own.

What’s up next for you? Perhaps a pair of Tungsol 6f8g round plates?