+1 for Raytheon VT-231’s! The Ken-Rad VT-231’s have the most solid bass of all the 6SN7’s I’ve heard in my Cary SLP05, Schiit Freya+, and Schiit Saga. The 5692 versions are smooth sounding. My favorite combos now are a quad of Raytheons in the Cary’s gain stage with by a set of CBS Hytron 5692’s in the XLR input buffer. With the Freya, black glass Ken Rads in the gain stage followed by the 5692’s in the buffer is my favorite combo, and I use a Sylvania 6SN7 GT JAN (“Bad Boy”) from the early 1950’s in the buffer.
I have a quad of NIB red base GE 5692’s (RCA made) that I can’t wait to try as well, with several other JAN versions of RCA, Sylvania, etc.
For the money, the best I have heard are 1960’s NOS Sylvania 6SN7 GTB’s bought for about $35 apiece from Brent Jessee that have an exuberant, sparkly top. They sound significantly better than any of the new production tubes that I have experienced.
I can’t recommend Brent Jessee enough, and will add that I have not yet experienced a bad experience buying NOS or used tubes from a variety of folks on Audiogon or US Audio Mart. I love the tonality of the 6SN7 tube, finding it to sound more natural and less hard than any 12AX7 tubes that I’ve live with for over 45 years (my favorites were Dutch Amperex, less dark than Telefunkens in my SP6B and Marantz 7C, as well as GE 5751’s used in the phono section of the Marantz).
