my tube configuration

[Ryanx]

i'm running what might seem to be an awkward tube combination.  at first i was running 3 ruby 6550's and one ge 6550, that's what was shipped to me, in the preamp section it was 3 ruby 12ax7.  since then i've replaced the ruby 6550's with an old tung sol and 2 more nos ge's.  i also the 12ax7 in what i believe to have been the phase inverter spot with a fender 12at7.  what other tubes would be good to run in the preamp to get a very clean tone.  i love the sound of my model t for sure, just looking for different tube combos.  when i changed out the 12ax7 for the 12at7 i noticed an immediate change.  debating now wether or not to go ahead and buy 2 more 12at7 tubes.

[EdBass]

I think tone is in the ear of the beholder. Like the opposite sex, what's beautiful to one may be heinous to another.
But generally, the less preamp gain the cleaner the amp. A 12AT7 has a gain factor of 60 to a 12AX7 gain factor of 100. Try putting the AT7 in V1 and see what happens. Keep in mind, your amp was probably designed for AX7's (I don't know what your amp is) and the lower gain may cause the power tubes to saturate at lower percieved volume levels. I think AT7's are about as low gain as you want to go.
Again, I'm refering to my definition of "clean".*
Speaking of power tubes, I assume you have a push pull output stage (it is a Sunn amp, right?). I think a matched, properly biased quad of 6550's/KT88's is a very influential factor to a clean strong amp.

ALSO, a strong power supply is mandatory. Weak filter caps can defeat any tube configuration.


*Your results may vary. Many factors contribute to harmonic distortion levels in a given circuit.

[Ryanx]

i have a 1973 model t

[SunnBurn]

Try a good NOS JAN 5751 (JAN Philips or JAN GE) in V1 and a JAN GE 5751 for the phase inverter.