Current production Gold Lion KT-88s suit my taste.
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"The inputs are what I'm most interested in"
Are the Sovtek 12AX7's the AX or the LPS version? Generically speaking the LPS version isn't far off from the tone you are looking for, i.e. open mid range - brighter highs, but how it combines with the EH power tubes, I don't know.
Another recent production tube for open mid-range and brightenened highs is the EI12AX7E (grey plate) if you can find them. A candidate which is easy to find is the Tung-Sol 12AX7. The Tung Sol has a bit more bass than the others.
Reconsider the power tubes you are using. I've found what you are looking for in SED KT88's or the more linear SED 6550. But there are a lot of options! Gold Lions are highly though of. I like the Tung Sol 6550's which are similar to the SED 6550's but with more bass/warmth.
Now for an unconventional recommendation. Based on my present use of them, SOVTEK KT88's. Excellent mid range and highs. Clean, clear, linear but not hyped up to impress. But a tad short on deepest bass but otherwise excellent. Not expensive. Rugged. Unless your amp is already short of bass and you need to plump it out or you are a loud bass person, these tubes can really do the job.
A caveat however, you may still want to change the small tubes to dial in the exact tone you want once you have decided on power tubes.
I have the same or similar amp (mine is the Signature), here is what I am currently using.
GL KT88 reissue power tubes
TS 12AT7 cryoed p-splitters
Baldwin branded 12AX7
I also tried the new GL12ax7, more of a sweet tubey sound. I prefer the Baldwin AX7's sound, more 'neutral' balance.
TS12ax7 (cryoed)+TS12AT7(cryoed) + GLKT77 was the ultimate balance for my taste. Excellent midrange, clean highs, and solid punchy bass. If you go this route request "hotter biasing' GL KT77 quads from your tube dealer, I rec. Jim McShane for the power tubes.
I got the cryoed tubes from Cyroset.
If you have 1000 hours on the amp, the degradation of sound is only due to the output tubes. 12 series tubes easily last 5000 hours and can go up to 10,000 hours. Output tubes will show wear at 1000 hours.
My advice, replace the outputs only and see how it sounds. Before replacing the 12 series tubes, get them tested. You may want to consider NOS tubes for these but tube rolling is the only way to find out.
Thanks for all the help. I just picked up a set of NOS SED 6550 "c" tubes from my local electronics house. He said they have been there for 15 years or so.
They are matched and according to him have about 30 hours on them.
I also found some Baldwin 12ax7 and some black sable 12ax7 that he had laying around. He matched all the tubes for me. All that for less than $100cash.
I will be putting them in this weekend and doing a good burn in of all the tubes
and see what I think.
My old ax12 were tested and one was below the well good bar. So one channel was sounding different.
He said he will look around to see if he can also match some KT88's for me.
I am looking forward to burning these in and giving them a listen.
I will let you know what I think.
Thanks again for the help.
So after about 100 hours on the SED "c"6550 power tubes with some Baldwin AX127 inputs here is my conclusion.
The overall sound is a bit more plump all around, not as colored. The lower octaves have opened and have more depth. The mids are fuller and more pronounced without being "in your face" full. The higher octaves do not seem to roll off as much as with the EL 34. Not quite the "crystal" sound that I was looking for with horns and piano.
With blues,some old jazz and deep female vocals it is just the ticket.
It has really made the sound more alive without being to edgy.
Stevie Ray has come alive and Stevie Wonder has taken the edge off.
Etta James is killer with her vocals.
Pink Floyd is not as sharp but more dynamic.
So far I am pleased with the sound on this roll.
I have a few other input tubes I will be trying in the near future along with some NOS JJ kt88's.
Thanks for all the help.