What Are The Best 12AT7's and 12AX7's?

Considerable improvement with the right tubes. I also bought Mullards from Kevin at Upscale. At that time I had a Prologue Three it was night and day difference. Good Luck.

I can't comment on 12AT7's because I never had a piece of gear that used them.

I have in my 12AX7 collection over 50 pairs of tubes from all the European and American companies. Famous Mullards, Amperex Bugle Boys, Telefunkens, Mazdas, etc.

If your piece can use 5751's I have found no tube that offers the sound of music better then these two: 1) Sylvania Gold Brand 5751's either gold or silver pins. 2) Mazda 5751 chrome plates.

They are not inexpensive, but not horrible expensive, and are so much better then even the highest regarded standard 12AX7's regardless the maker or time era. The Mazda's are very hard to get,but you should be able to score the Sylvania's. Remember not just Sylvania, but labed Sylvania Gold Brand 5751's.

agree with above

the 4004 have a big, golden sound that is very pleasing.

Of course it is pretty hard to predict what anyone one person would prefer sonically, so at best, we can only make some recommendations on what to try.

I agree that 5751s are worth trying. They have lower gain than 12AX7s, however, so they may not be true drop-in replacements. I don't know if it is true, but, I've read of instances where the difference in gain adversely affected the phono equalization.

If I had to pick one tube as being almost always an improvement over current production tubes (i.e., a universal upgrade), I would pick an Amperex Bugle Boy 12AX7. These are expensive, but, they deliver a rich, full-bodied sound without being murky or sluggish sounding.

I have tried a pretty wide range of 12AX7s and 5751s in my phonostage. For my particular taste, and given the other components in my system, my personal preference is for the Telefunken ECC803S. But, I can see how this tube would be too lean and aggressive sounding for some systems. This tube is on the opposite end of the spectrum from something like the old Mullards.

My Vote is 12at7 Phillips Miniwatt ( Herleen version ) and Sylvania 5751 3 Mica Black plates..Good match using these together also..Been using them for years in my Thor Linestage.........