So, here is my 'blast from the past': Tonight I fell in love with my LD Mk IV all over again!!
My 6SN7 adaptors arrived tonight, so I finally got to try some totally new power tubes!! The only ones I have right now are 1955 Sylvania 6SN7GTB black plates ($25)... but wow, they sound beautiful!! Biggest improvement from any tube (driver or power) I have put into this preamp!! I am deft going to stay and play with 6SN7s for a while. I have some Russians on the way and I found a great price on some Mickey Mouse ear Tung Sols ($22)...
On another note, my current drivers are some Russian 6J3P-Es marked OTK <0> ($8.50 for 10!!). Lampizator says zero in rhombus is 'space'... which I tend to believe. They came with the best packaging of any Russian tube I own, each with its own data sheet. They sound very nice with these 6SN7s... but I'm going to have fun rolling some other drivers. Can't wait for my C3g/s to arrive!!
Thanks again to you all for finding the path!!
Best,
G