By the chance, did anybody tried Japanese stuff? ….Hitachi 12AX7, NEC 12AU7, Toshiba 12AX7 or Matsushita 12AX7 ?
Vintage Japanese tubes are excellent and I will give you one unique example from my vaults (images taken by myself, use links below before they will be expired).
These are very interesting preamp tubes from Japan (new old stock from the ‘60s). The wonderful "sleeper" in the world of 12AT7s for me are old Japanese tubes. National is a trademark of Matsushita Electric Industrial Co., Ltd. If you’re set on the sources and still want more tubosity- nothing beats old National (Matsushita) with pinched waist glass and gold pins.
The most well known pinched waist tubes are from Philips Heerlen and Valvo Hamburg. They were made mid to end ‘50s and have the glass pinched around the top mica spacer. I assume this was done to fight microphony. Pinched waist tubes have an indented ring around the middle portion of the glass tube. They’re quite expensive, but not overpriced like Mullard or Telefunken tubes from the same era. I’ve noticed that tubes from 1958 and earlier have a bigger pinch then tubes from around 1960. Personally. I haven’t seen tubes after 1960 with a pinched waist.
P.S. Tube rolling was fun in my integrated amp (I do not use tube phono stages). I’ve been looking for the best 12AT7 type (but not the most expensive as I already had genuine ECC801S Telefunken with diamond glass base).
Japanese tubes are normally cheaper and cheaters do not try to fake them! Most people know nothing about Japanese tubes. If you want to find something use Tube Asylum forum.
Matsushita tube factory in Japan was set up by Mullard!