Nice review of 5751 breed. My coments are from listening on two '5751/12AX7 driver based systems (Sherwood S5000 and CJ-MV-52), as well as in Cal ALpha DAC driving these and ASL KI15 FOX, a SET IA (killer value). Variety of speakers (Celestion SL6Si, VSA-VR3.5, Monitor Audio, Kestrel).
I agree specifically with your notes on the Tung-Sol ('50s bent-D getter, long grey plate)and Sylvania 5751 3M-BP, GB or other. The latter is my choice for a desert isle, followed by, in a forced decision, TS versus GE (I lean to 'air' when forced).
For some reason, I am less enchanted with the Raytheon (3-mica BP). Though excellent as you describe, it does not to my ear have the character of the others. Very competent in all regards, however, nothing to dislike at all. Just no standout features, comparatively.
Also, I was not bowled over by Syl 5751 3M Grey Plate (WA version), a bit too diffuse for me, though has it's charms for sure, esp. for vocals, where it shines like no other. Much better than JAN versions of this tube, though.
The one I would add to the top three would be GE 3M- shiny BP from the '50s. In fact, these look almost identical to Sylvania GB--slight differences in width of plate flanges (wider in Syl) Not as much air as Tung-Sol, but better body and balance. Second to Sylvania 5751 (WA or GB black plate). Not as extended as Sylvania, but more body and warmth without compromise to clarity. More complex character when 'looking into stage'. Sylvania comes to you.
Three 12ZX7s that compete for top five slots, IMO:
Raytheon 12AX7A ('60-'61)--an odd '2.5 mica (retaining ring for top mica in this version)' 12AX7 type. Similar to Sylvania GB, not quite as well balanced, but, for dark amps (vintage) may be perfect. It displaced Sylvania GB from V3/V4 in my Sherwood S5000II (a honey of an vintage IA), but not in my more resolving CJ-MV52. Was close to Syl, though, for a couple of days.
Tungsram 12AX7 (Hungary, Yellow Print '70s): In my Califonia Alpha 24/96 DAC, this is the best I have tried. Transforms this DAC. In a bright system, however , could sound a bit 'fizzy'. The widest stage of all the tubes and best air. Transformed the sound of my Cal Alpha-CJ system--even with bright Monitor Audio Silver 9i.
Mullard CV4004 (83-85). VERY nicely balanced and extended, similar to GE 5751 with great body. Less air than the best 5751, but better balanced than Tungsram or Raytheon 12AX7. Great in Alpha DAC, better than rest in my circuit, until I tired the Tungsram 12AX7.
Amperex 12AX7 is also quite good--like the TS, but missing some clarity. Lively tube.
I agree specifically with your notes on the Tung-Sol ('50s bent-D getter, long grey plate)and Sylvania 5751 3M-BP, GB or other. The latter is my choice for a desert isle, followed by, in a forced decision, TS versus GE (I lean to 'air' when forced).
For some reason, I am less enchanted with the Raytheon (3-mica BP). Though excellent as you describe, it does not to my ear have the character of the others. Very competent in all regards, however, nothing to dislike at all. Just no standout features, comparatively.
Also, I was not bowled over by Syl 5751 3M Grey Plate (WA version), a bit too diffuse for me, though has it's charms for sure, esp. for vocals, where it shines like no other. Much better than JAN versions of this tube, though.
The one I would add to the top three would be GE 3M- shiny BP from the '50s. In fact, these look almost identical to Sylvania GB--slight differences in width of plate flanges (wider in Syl) Not as much air as Tung-Sol, but better body and balance. Second to Sylvania 5751 (WA or GB black plate). Not as extended as Sylvania, but more body and warmth without compromise to clarity. More complex character when 'looking into stage'. Sylvania comes to you.
Three 12ZX7s that compete for top five slots, IMO:
Raytheon 12AX7A ('60-'61)--an odd '2.5 mica (retaining ring for top mica in this version)' 12AX7 type. Similar to Sylvania GB, not quite as well balanced, but, for dark amps (vintage) may be perfect. It displaced Sylvania GB from V3/V4 in my Sherwood S5000II (a honey of an vintage IA), but not in my more resolving CJ-MV52. Was close to Syl, though, for a couple of days.
Tungsram 12AX7 (Hungary, Yellow Print '70s): In my Califonia Alpha 24/96 DAC, this is the best I have tried. Transforms this DAC. In a bright system, however , could sound a bit 'fizzy'. The widest stage of all the tubes and best air. Transformed the sound of my Cal Alpha-CJ system--even with bright Monitor Audio Silver 9i.
Mullard CV4004 (83-85). VERY nicely balanced and extended, similar to GE 5751 with great body. Less air than the best 5751, but better balanced than Tungsram or Raytheon 12AX7. Great in Alpha DAC, better than rest in my circuit, until I tired the Tungsram 12AX7.
Amperex 12AX7 is also quite good--like the TS, but missing some clarity. Lively tube.