here you go.
plucked from an archive i made for my own personal ref.
hope this helps.. its pretty much accurate in in layman's terms
the only thing i'd add.. rather is v6 is more technically --- the phase inverter tube. 12at7
-- i like a nice military spec tube for this spot --- it's not directly dealing with gain so much
as it's dealing with actually inverting phase of the signal before output stage... Check out
any tubes labeled as JAN or anything labeled 12at7wa
FYI: 7025 is just another way of saying "12AX7" or low-noise 12AX7 -- (*low noise)
v1 v2 v4 are going to be where you want to put your BEST tubes you can find..
if you never use the normal channel and plug into the vibrato input --- Then v1
really won't matter as much.. and i'd save the spots of v2 v4 for the best tubes..
then again, if you only use the normal channel.. then v1 is certainly your most important
tube in the pre-amp section.. mix and match.. experiment, you can pull v1 out of the socket
all together and push v2 harder for earlier breakup (but obviously it will only work on the vibe input).
v5 is not important.. so don't be foolish and waste a mullard in that spot.. go have fun (hope that helped)