tell me more
. I’m not familiar with these tubes. Are they worth 60+ a piece?
Depends how bad you want them, I've gotten one for $1 and a pair for $75 (total of three on hand) and one of our Headphoneus Supremous (
@bcowen ) members here has dubbed them, ordained them... The FrankenTube. This from Bcowen
"This is long (sorry), but skipping to the end won't do any good because I put all the important stuff in the middle.
In my never-ending quest to find the perfect tube for the Lyr, and even after realizing such a thing doesn't exist I started looking at 7N7's. Firstly because they're electrically identical to a 6SN7 (basically a 6SN7 with a different base), and secondly because they're cheap. Like me. I started with a pair of Tung-Sols -- $20 bucks for the pair delivered. After a day's worth of break-in, I liked them. Liked them quite a bit, actually. Strong bass, very dynamic, and a sparkly treble. Very nice tubes period, and really nice tubes for the money. But at the end of the day they were just really nice tubes, and not in any position to unseat a Bad Boy, WH D, or even my beloved Fotons. But I was intrigued, and bought a pair of CBS ($18 delivered) and then drained the bank account on a pair of RCA's ($28 for the pair). Honestly couldn't tell a lot of difference between them and the Tung-Sols. All of them nice, none of them groundbreaking. As I continued my research, it would seem that there were only two manufacturers of this tube type: Sylvania and National Union. There is so much conflicting info out there it's hard to tell who's right and who's not, but the dual-manufacturer status of these is prolific among the more reputable sources. After looking closely at these three different tubes, it became obvious why they sounded so similar: they're identical internally. Not sure if they were made by Sylvania or NU, but it's clear they were made by the same manufacturer. After more searching I ran across a number of different forum posts from all over that mentioned the tall bottle versions of this tube type sounded better than the short bottle ones. As the tubes I had were all short bottle, I ran across an Ebay ad for the tall bottle pictured below. And the rest is now history. Powerful bass, dynamic and punchy, a midrange that's *just* right, beautiful treble, the rhythmic drive of a Foton. But there are two things that are remarkable with this tube: imaging (or maybe soundstaging) that locates each performer or instrument in its own acoustic space. You can pick out the individual voice in a chorus and the 3rd violin from center in an orchestra. And you hear the space surrounding them. I haven't heard this space-reality thing with headphones before. Not even close. And then there's the tone. Holy friggin' crap. Tone. The depth of harmonics and the full fleshing out of every resonance and micro-detail in the note. If you're a rocker or metalhead and love the sound of an electric guitar or bass, you'll turn into one great big goosebump with this tube in the Lyr. I even listened to some jazz...and liked it. That's never happened before either. I rarely gush on a tube because a lot has to do with personal preference and system synergy, so I won't gush over this one. I'll just say that even after several reality checks swapping a Foton or WH D back in for comparisons that the Frankentube is now my personal reference and owns the #1 spot by a pretty wide margin.
Frankentube? Well, had to name it.
Not all tall bottle 7N7's have this magic. What's notable is the shape of the top of the glass bulb -- it's 'squared off' like the top of Frankenstein's head (or was that Herman Munster)? There are tall bottle versions that have the more rounded top shape, and they don't sound nearly as good to my ears. This is the Frankentube:"
https://www.head-fi.org/threads/schiit-lyr-3-tube-rolling-thread.876016/page-84
i rarely see these posted for sale so when I see them I share the links