12ax7 vs 5751

I've been through experimenting with 12AX7 and 5751 tubes. Gathered a lot of them. Everything you want to know is in this excellent reference :
http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html

Second Andr, Joes Tube Lore gives a great summary. I have Sylvania 5751s Gold black plate that made a huge difference in one of my amps; but always trust your own ears.

I am impressed with your choice of 6SN7s. I really like the Brimar CV1988 GTY. See if you can get some Sylvania GTs or Ws as well for 6SN7s. Given your choices with them I would definately recommend that you look into 5751s.
I find 5751s to be more defined and yield better soundstage in my applications. I agree that there are more good ones floating around than most NOS 12AX7s. I also say you should look into it- as no one can assert with certainty what you will like. I have a hunch you will like them. Sylvania triple mica BP are prolly the best but failing that, try some TM BP RCA white lable, Raytheon in general, (yes windmill getter but they are rare) then perhaps lastly GE with some special GE vintage exceptions. The militery versions of all are good.

wow thank you guys for the wealth of information. the psvane tubes i`m currently using sound just fantastic but i`m sure they`re limited in the soundstage width and depth. i`ve played around with all the other tubes and so far the brimars have had the best results in the soundstage and tone but i`m looking for more depth in the soundstage. thats really why i`m looking into the 5751 range of tubes. i`ve read good things about the soundstage they throw out. tonally i`m extremely pleased with the range of tubes currently in my amp but like everyone out there, if the sound can be improved upon then why not indeed. you only live once! i`ve been considering getting some sylvania 6sn7gt`s too to mix with the brimars. i think the wgt`s will have too much upper attack for my system but i have my eyes on a matched pair of sylvania bad boys. the gtb`s that i`m using right now seem to go hand in hand with the brimars tonally. voices are amazing! i tried the brimars with a matched pair of rca vt231 grey glass tubes but it was an awful match. too much warmth to the point of making it sound dull. i had such high hopes too for this matching.

joes tube lore is making for a very interesting read! i think i`m going to be having a lot of fun experimenting here with different tubes.

i`ve got to say too......i`m having the time of my life listening to different tubes. this being my very first tube amp! i`m impressed at all the different qualities each tube brings to the amp and all the fine tuning that can be achieved. the amp sounded good enough with the standard tubes that came with it but the amp was secondhand and the tubes were very noisy!

also when the psvane tubes were breaking in i was shaking my head in disbelief in the 1st 5 to 10 hours! the sound changed quite a few times! everytime sounded good with the exception of a couple of times the sound seemed to come out of complete darkness and that blew my mind! wish i could get that particular sound back! but thats not really a complaint as i love what i`m hearing now

another thing i must add......i seem to sit there now listening to music with a big stupid grin on my face most of the time! what a way to escape the stresses and strifes in this life!