I have got so meany tubes for my Little Dot III .
The best are the Rocket Vishods EV 1980-1985 with the fluted glass, The Mullard M8100 is good but I like the RCA and GE 5 stars top end better than the Mullards .
The Power tubes made a huge difference too, Best sound for the Money is Cryo treated EH 6H30pi.
The MKIII just has a nice simple circuit that works, and the tubes seem to last forever.