Svetlana's (6550 C), but that was prior to me knowing much on tube makes.
I soon afterwards found out the Svetlana's can be pretty touchy (poorly made)
Im pretty sure there is something a bit different about the head too, but, it was away for about 2 weeks getting revalved and such (there were a few problems, i got it all checked out incase there was anything else wrong, but it was just a dead power tube).
I was given a chance at some NOS RCA's for a really good price, but, they had gone a bit soft apparently, so i thought best not to go with them.
When i have a chance to revalve, im going to consider JJ's, EH's and Sovtecks.
I know its not needed, but there is a niggling whenever i use the amp, something in the back of my head expects it to die at any moment

(but its not, seems to be solid!)