in the affordable range here is my rating, based from smooth to high gain sustain
starting from a mellow mullard 12ax7
this is one of the worst sounding i think....
next would be the grouping of high gain high handling smooth sustain
these are all expensive and offer little to no need, but some people can hear the different in modded super texans and princetons...
next are the tunes from regular handling to all out handling
jj 12ax7 for a smooth flat slow responce, usually a fav for marshall amps
there are a couple types, old tesla spec and new spec, either way they suck and arent worth the money
a sino 12ax7 tube i beleive is WAY better and cheaper than a jj
next would be a sovteck 12ax7 in that range with better response qualities
next would be OLD NOS version of mullard, amprex and telefunken but they all range from 100+ dollars a tube! and arent worth it unless you like them, they do have a sweet tone to them - but are pretty out there, i cant tell between them and a new production mullard
origional raytheon, black sables, and rca/ge...like made beofre 1960's these are still the best i think for clean tone but all range from 300+ per tube, CAN be worth it, but not for me
then on is the most common and probably the best ones made curently
eh12ax7(high gain rating)....these guys make exceptional new tubes, great responce, great material, great heat handling and AWESOME structure and feq matrix between the grid from emmiter to collector
i would suggest getting this one in the high gain tested version, ONLY. BECASUE the tube handles better, more headroom, no flattening of signal responce, and improve gain structure between tubes.....very smooth but also shimery
next is the new tung sol 12ax7, i suggest you read about this one, if you want a clean ultra responsive signal this is where it is at. some old tungsol's are actually not that great, they have the same type of tone te new ones have but are more closely relted to the ge 300+ dollar tubes with that clean bass responce..its just a different material in it
but for the most part i in love with the tone of tung sol, i can drive MEGA bass into it from my preamp and it wont mudd out and take over the mids or the highs, makes it a very tight super tight responce and shoves the bass down delaying it so the uppers are more present, but the bass is still thick
now its a decision as to where these tubes go
for your preamp, lets say you have a mesa preamp unit or a digitech 2120 or a vox tonelab
these all are preamp units only no poweramp
you should use a more tonaly stable tube for the preamp section where your tone matrix is at....being able to use a tube that has a natural level between bass mid and treble is where the zone is..i still suggest a eh12ax7 high gain version for all of this
now for poweramps, there is usually a couple of PREAMP tubes in it, just like the carvin rack amp, peavey rack amps, engl, etc....for these your two options are smooth dead responce, out in your face, shimmery fast reponce...
these two decisions are entirely on tase just like a powertube
i suggest for a slower mid sound responce maybe for a acdc tone well choose anything from a quality eh to a lower quality sovtek or even a mullard type...but if you want to drive your powerstage and get full charachteristics from those power tubes, were talking about a tungsol 12ax7, wich also increases gain, headroom, freq responce etc...this is like putting he output stage on crack, and getting all that jiuce into the tubes.....
remember....the volume of an amplifier is not entirely corrolated to the wattage
it is solely based on the responce of the amp
the faster the response between the tubes and the circuit
the faster the tranny operates
that harder the speaker hits
tubes also add other things, hopefully this helps...but its just a ballpark responce