Listens2tubes, Yes I have, I have 4 pair of 801s and 6 pair of 81s all from the same time 1967 and I really can't hear any difference between them, in the 550 or the T-DAC or the T-5

but I have a pair of Telefunken ECC81s from 1960 that seam to me to make the set sound better when I run them in the T-5.
