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12ax7 vs 5751

hi all,
i need some advice. i`m very new to tube amplifiers and i`ve been doing some tube rolling.

i currently have a pair of grant fidelity matched psvane 12ax7t`s in my amp which sound fantastic.

what i`d like to know is which are the better tubes, 12ax7`s or 5751 tubes. i`ve been looking at forums and there are folk out there that say 5751 tubes are better than 12ax7 tubes.

can i have your thoughts on this please and also which are the good 5751`s to go for.

i really like the psvanes but if they can be bettered i`d go for it as my next line up of replacement tubes.

my amp is a yaqin mc100b. the tubes i have installed at the moment are.....
2 x psvane 12ax7t`s
2 x brimar 6sn7gty/cv1988`s
2 x sylvania 6sn7gtb`s
4 x electro harmonix kt88eh`s

many thanks in advance guys.
grayf
cymbop
315 posts
 
It's not possible to generalize one as better than the other. They are interchangeable, though the 5751 has a gain rating that's less than the 12AX7. I run 5751s in my 12AX7 slot and can hardly discern less volume. Because the 12AX7 is so common, it's more sought after and as a result old stock models are more expensive. 5751s fly just a little under the radar and so you can get good ones at a better price.
grayf OP
61 posts
 
many thanx for that info cymbop. thats pretty interesting information there. it`s well worth me investigating the 5751`s in the future
andr
109 posts
 
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
mikirob
955 posts
 
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.
mechans
3,048 posts
 
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.
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