Forgot to mention one of my all time faves:
Raytheon 12ax7
At least I think what I have is Raytheon. It has long shiny black ladder plates, and halo getter. Gold labelling on mine is "Baldwin Piano-Organs, Made in USA". My understanding is that Raytheon made them for the Baldwin company for use in their organs. I believe "Schober Organs" also sourced theirs from Raytheon and you will sometimes find them labelled that way.
There are some variants out there with the organ labels, but perhaps sourced from Sylvania? I have also seen grey plates, square getters, and green labelling. I can't comment on how they differ from mine.
Don't laugh. This unassuming (and cheap!) tube has at least equalled (and often bested) all the good European ones that I have tried in both my phono sections. I think it ranked #1 in a 12AX7 shoot-out conducted by Vacuum Tube Valley magazine. This USA made black plate Raytheon beat out Telefunken, Mullard, Amperex and all other makers and variations of 12AX7 tubes for the best audio!
Prepare yourself for a plush ride with these babies! These Baldwin tubes have quite an amazingly strong personality: rich, full, deep, lush, 3D- a lovely, vintage sound. There might be a slight give-up in detail and treble resolution/extension, but they are wonderful if you like a really liquid, smooooooooth, and deep sound. They really do all the things tubes do quite well, but just with some extra depth and smoothness. Hence, maybe not the most dynamic, but the bass is still strong and has good weight...but maybe not as clean and punchy as what more "accurate" and modern tubes would give. The midrange is VERY nice....think Crosby and Sinatra.
I use lush and vintage in a good way here. Not thick, dark or overly obscured. They sound just right to me. Quite well balanced with nothing sticking out. Good clarity without any glare on insistent quality whatsoever. Naturally detailed, smooth and relaxed. Wonderful tone and organic quality to the sound. A nice "wet" soundstage that is wide and deep, and populated by focused and believable images. Very quiet and not microphonic at all....even when tapped.
This tube never fails to draw me in and connect me to the music. Very musical with good "pull". My experience with these in my phono section is that I just forget about the gear and concentrate on the music more.
Were I you, I would start with this one. I wouldn't be surprised if your search ended here. And the best part is...they are insanely cheap! I got mine on E-Bay. The seller was not a pro tube seller....just a hobbyist. He stumbled upon a stash, kept enough for himself, and sold the rest. He told me they beat all his top Teles, Mullards, etc. I figure sure, sure.....sales pitch. But sure enough, I see all his used "big boy" 12ax7 pop up on E-Bay. I took a chance and am glad I did. Do a search on "Baldwin 12ax7" or "Raytheon 12ax7" (or maybe "Sylvania 12ax7"?). There are some there now.
re: Sovtek 12ax7-LPS
while it is decent and pretty good as far as current production goes, its performance is fairly pedestrian and unspectacular. It is listenable and pleasant because it is not shrill or bright like many CP tubes. I've tried it in several pieces of gear and hear it to be just a bit grey and flat...lacking in space, air and dimensionality. This Raytheon....and most other good NOS...beat it handily.