Time for new tubes.. which ones?

I own a TAD-150 and have tried various brands of NOS and used vintage 12AX7, 5751, 12AT7 and 12AU7s from the US & Europe. Right now I am using RCA blackplate 12AU7s. These tubes have excellent bass characteristics and do everything else very well. Another bonus is that the volume knob has much more play in it. 12 o'clock is now very loud insted of 9 o'clock. The 5751s would be my second choice. Good luck in your search.

The 12AU7s have less gain and that's why you have more precise volume control which will likely result in better channel tracking. Aside from the TAD thread, you might also check out the detailed descriptions of the various brands of 12A?7s available from Joe's tube lore at Audio Asylum. You will have a bewildering array of choices since there are probably a half dozen variants of each of those basic tubes and usually multiple manufacturers. One thing you should think about is how much is appropriate to spend on NOS tubes for a modest cost unit. For example, I think that the Gold Pin 5751s are now going for well over $100 each!!!

I replaced the stock tubes with Groove tubes 12AX7s from Upscale Audio. Reasonable price and nice improvement over the stock tubes.

I just ordered a few different pairs of tubes for my TAD-150 to try out.

Cryoed Sylvania 5814A black ribbed plates NOS
Cryoed Sovtek 12AX7LPS NIB
Cryoed Tung Sol 12AX7 ECC803S Gold Pin NIB

I'll post when I have checked them out.

Also head good things about the JJ/Tesla 12AU7 ECC802 Long Plates.

Tube progression, so far....

Stock t7-flat sounding, rolled off top and bottom lack depth and width of soundstage
RCA x7a ribbed gray plate-better than stock
RT u7wa-ribbed gray plate-better than the RCAs but one was a bit noisy (couldn't stand it, wish I could have listened longer)
Brimar u7wa-gray ribbed long plate-better than any above-wider soundstage, increase in bass
Sylvania JHS 5751-wow, a direct hit, improvement across the board-Very nice soundstage width and depth, plenty of detail and prat! Gain match with volume control into my Mc DNA-125 is right on.
Mullard x7-short plates, halo getter-A MAJOR DISAPPOINTMENT-detailed but very flat-lost the soundstage completely (I hope everyone does not read this thread because these will be for sale soon!)
GT ax7m-playing now, just got them today-These are nice, very, very close to the 5751s mentioned above. They may lack some of the fine detail of the 5751s but not much. I can live with either.

I would like to try some nos 50s long plate Mullards or Telefunkens but I got to agree with Swampwalker, it seems a bit crazy to put $100 plus tubes in this pre (or does it?). For $50 a pair or so the 5751s or the GTs would seem hard to beat.

I have never fooled with cryoed tubes so I would be interested to get Stratosaur's impressions...