Tube favorites for Modwright LS100?

For the 6SN7 I'd give the Shuguang CV181 Black Treasure tube a shot. These take a bit of break in time and in my experience will fluctuate widely in performance in the first few hundred hours, but the stable performance after that will be worth the patience. I do not have experience in that preamp though. You might be able to find a used low-hours pair for $150 or so. There are some NOS Russian variants that are quite good too, but their prices seem to be going up dramatically lately...I think the pair I have that I really liked is a metal-base 6H8C with round-hole plates. The plastic base version of the same tube is also pretty good and cheaper. As far as the rectifier tube, a sleeper tube in that family is the GE copperplate. You might also try a 5U4G, like an NOS Tung Sol in there as I think you can use that tube family as well.

Thanks friends for your thoughts. I must admit a certain fascination for the Black Treasure tubes, even though they are obviously a bit dear in the British sense of the term. I should perhaps not be so brash as to completely discount the reported superb sound quality of the best available vintage tubes, but is the often very high cost of admission really worth it?

I preferred the Black Treasure tube in my MWTP over the very dear NOS TungSol round plates. I also prefer the Black Treasure in a headphone amp I'm testing out right now, compared to the same TSR. Go figure. I did not like the Black Treasure tubes right out of the gate though. I think you'll find there are bargains to be had from those who don't give them enough time to burn in and just sell them out of frustration. I have not tried any of these tubes on the LS100 you own though so take this input with that caveat.

Hi Bob,

I have used the Black Treasure KT-88's and I like them very much but never tried the CV 181. You might want to try the Chinese 6N8P-J military tube. They work well in my pre-amp and they are cheap.

I have received a pair of Shugang Black Treasures and put them in the LS100. Below is the email I just sent to Dan Wright and Grant Fidelity...

I received the Shuguang CV181-Z (6SN7) Treasures and a NOS 5AR4 and burned them in for a few hours yesterday. Even though the LS100 and the tubes have only a few hours on them, I was quite unprepared for the sounds I heard during my first listening session. For the first time in my audio life my speakers literally disappeared, and the imaging filling my room was almost palpable...very 3-D indeed, to the point of being almost scary-real. I sat in wonderment; left wanting for nothing with the music being produced with such crystal clarity and startling precision from top to bottom. I can only anticipate what further improvements may happen as both the preamp and tubes continue to settle in together.
To be brief, my searching for the next best preamp is over, as is my searching for the next best tubes to put in that preamp. This combination has taken my humble audio system from good to "wow"!
Thank you Dan for designing such a wonderful preamp at such a fair price, and thanks also to Shuguang for producing a pair of tubes that have taken that preamp way over the top in audio quality. Job well done!