Retubing a Twin

[GuitarJonz]

Got a SF Twin with the following tubes: (4) Sovtec 6L6, all Ruby 12ax7 and 12at7, with the exception of (1) Mesa 12ax7. I assume that much better tubage is available, what is recommended, within reasonable cost? Also, I think I have a few better US made 12ax7's and possibly 12at7 in the drawer here, which tube slot should they go in for best effect?

[Ringo]

What you have may not be bad really, some of the Chinese made Ruby 12ax7's are great, I bought some from Lord Valve a couple of years ago and have been using them in my 68 DR for a while now, they sound fine.
A good friend of mine has been running Sovtek 5881's in his Super Reverb for about 10 years and it sounds - well Super!

for most 2 channel Fender amps with reverb and tremolo the order of preamp tubes is something like this

#1 - 12ax normal channel preamp
#2 - 12ax7 vibrato channel preamp
#3 - 12at7 reverb driver
#4 - 12ax7 1/2 Vibrato channel 1/2 Reverb Recovery
#5 - 12ax7 Tremolo - you don't need a real "good" tube here
#6 - 12at7 phase inverter

It's easy enough to swap some preamp tubes out and see if you like the tone of one over another better.
When you get into swapping power amp tubes though it may require the amp to be rebiased.

New production tubes ? The JJ 12ax7's are supposed to be good, and some folks like the Electro Harmonix 12ax7's which are supposed to be better than the Sovteks, I've used the Sovtek 12ax7wa's with good success.

NOS USA 12ax7's are still plentiful and can be gotten reasonably, even good used old production 12ax7's can still sound good and last a long time.

The audiophiles are into Mullards , Telefunken, Amperex and they can be $$$!
Not sure that they really "sound' better though, I have a few old Telefunkens that I have aquired over the years, I've been trying to compare them with old RCA's, Philips, Sylvania, Sovtek, and the Rubys to see if there really is much difference. So far it isn't earth shatteringly noticeable to my ears.

An amp tech who hangs out on the Weber BB's recently did a 12ax7 "shoot out" comparison for a tube magazine, the results are going to be posted on his website soon - http://www.unclespot.com/
I'll be interested in seeing how the new production stuff rated.

[Tremo]

For 6L6s, it's generally agreed that the best current production stuff is the JJ and Svetlana (flying C) brands.

For the 12AT7, the JJ and Sovtek are decent and will work well in that amp.

For the 12AX7, the JJ are good, but I really like the Sovtek LPS version. The Ei sounds sweet as well, but they have a LOT of failures.

For the 12AX7, I like ones that sound warm smooth and sweet. I personally find the Chinese to be too bright and grainy. I also find the Sovtek WA and WXT to be far too bright and brittle. IMO, for a cheap AX, the Sovtek WB sounds better than the WA or WXT. Still, the LPS sounds better yet.

[Ringo]

Maybe the generic chinese 12ax7's are grainy and bright but the Ruby chinese made 12ax7's that I got a few years ago are great tubes, to my knowledge they aren't available anymore, and the newer ones aren't as good.