changing tube postions

[fourmations]

hi all

i have a cracking old tube amp

the cleans and crunchys are super
but it gets very muddy when i up the gain

i am putting a few quid aside for a full service that it needs badly
but in the mean time........

is there any point in swapping around the order of the 12ax7's (there are 5)
is there any rule of thumb for this

the tubes are really old (possibly 25yrs)
and only one has any brands on it (a replacement i'd imagine, its a mazda)

rgds

4

[blacktiger]

The Mazda isn't neccessarily newer.  French Mazda tubes date back to at least the 60s.  It can't hurt to switch around the 12AX7s and see which sounds best in which spot.  Another option would be to switch the phase inverter (the 12AX7 closest to the power tubes) for a 5751.  It'll take the gain down a little, but it could also help with clearing it up and smoothing it out a bit.