5751 or 12AX7 characteristics?

[pennylink]

I have a chance of picking up a GE JAN-5751/12AX7WA.

• Can anyone clarify if this has the gain characteristics of a 'normal' 12AX7 or of a lower gain 5751?
• Has triple mica and black plates... so 1950's-1960's?
• How does it compare to a triple mica GE 5751 5-stars?
• Would you consider this one of the 'great ones' and suitable for PI, or would you recommend a different 5751 option?

Thanks!

[redshark1105]

I will answer the first question:

12ax7 amplification factor 100
5751 amplification factor 70

[pennylink]

Originally Posted by redshark1105

I will answer the first question:

12ax7 amplification factor 100
5751 amplification factor 70

I understand, however the tube has both 12AX7WA and 5751 printed on it

[Hand of Doom]

Those look like 5751's to me. I don't think I have seen a 12AX7 with triple mica spaced that way. Come to think of it, all GE black plates I have seen are long plate.

The 5751 in my experience is cleaner and deeper in tone than the 12AX7.

[pennylink]

bump for the tube experts

[Tomo]

Great thread!

Tomo

[slartibartfast]

thats a good 5751, by which I mean its well made. Whether you like the tone or not is up to you. What itll do depends on your amp. I've a superchamp (the real 80s one) that I use 5751s in. Its got a high gain preamp, and a 57 calms it down a bit and gives more headroom and touch sensitivity. Thats cause it hits the rest of the amp with less force. A 12ax7 saturates the amp and gets it into fizzy territory. I also have a blackface champ which is in no way a high gainer. The 57 in it gives more touch sensitivity and headroom, which is good cause I dont like the way it distorts. It also makes it nicely chimey. All up I like 5751s. They suit the way I like my amps to sound. It may be totally different for you.

By the way your tube is a 5751, regardless of what its got printed on it. Totally different plates to a ge 12ax7

[Ginglymus]

That looks like exactly the same tube as a GE five star triple mica black plate 5751. Very nice!

I love these and similar RCAs as 12AX7 subs. They give more drop in circuit gain than a 12AT7, due to their relatively high plate resistance, even though the 12AT7 has a lower amplification factor (60). And they sound better than 12AT7s in this situation. You might find it more useful in the V1 or V2 positions than in the PI slot. E180CC (7062) and 12AY7 (6072) are great too.

[Primakurtz]

Coincidence - I put one of these in the V1 spot in my Ampeg VT-40 today. Excellent - I can turn up the volume a bit more, getting into nice-but-not-fizzy breakup earlier.

[Hand of Doom]

Here are a few wanking clips of a Raytheon 12AX7 and a Raytheon 5751 in a Vibro Champ....

http://www.youtube.com/watch?v=MvPXAo5hINo <-- 12AX7

http://www.youtube.com/watch?v=uyj0EmOIMDs <-- 5751

[pennylink]

Originally Posted by sangre azul

Here are a few wanking clips of a Raytheon 12AX7 and a Raytheon 5751 in a Vibro Champ....

http://www.youtube.com/watch?v=MvPXAo5hINo <-- 12AX7

http://www.youtube.com/watch?v=uyj0EmOIMDs <-- 5751

Thanks for posting the links. You can clearly hear the difference between both tube types.

5751 seem to be used a lot in Fender style amps. Does anyone use them succesfully in Marshall or British-voiced amps?

[s360guitarist]

Yep. Excellent post. Been wondering lately what the 5751 would do to tame some of the ice picky harshness of my AC15...Thanks for the post!

[charveldan]

A 5751 is a great way to tame down the buzziness and gain of an amp.

Use V-1 the slot for your best tube [voicing] like a NOS Blackburn Mullard, Amprex or Telefunkin, put a 5751 in #2 and/or #3, then your PI tube, and you'll be cook'in with GAS>

J.A.N. stands for Joint-Army/Navy, these were tubes made for Military stock.

[Mike9]

I tamed some of my OD in my #40 Dumble clone with a 5751 in V2. A 12at7 had too much loss and a 12ax7 was too harsh for my tastes. I have A/C filament voltage in this amp.

Interestingly V1 in my Dumble clone is very hot maybe it's the A/C? I've settled on a JJ ECC83S short plate there as it's one of the few tubes I have that is not microphonic in that spot. I use a vintage Tung Sol 5751 in the V2 (OD) and a balanced JAN 12at7 for a PI driver with Shuguang KT66's in the power section. This amp is cooking nicely now the clean channel is excellent and now the drive channel is somewhat under control though I might try to curve it a bit more.

I tried about my whole box of tubes - Mullards, Amperex, Sylvania, RCA, and some moderns and found V1 in this amp to only like certain current production tubes - namely the JJ, 12ax7EH, a Silver Dragon 12ax7B and a couple of Chelmsford 12ax7's. All my vintage tubes were noisy but only in this amp's V1. They work great in all my other amps - must be the circuit - go figure.

[davebc]

I used 5751's in both my Victoria's. At first I was very skeptical concerned about there being no gain.
WRONG!
In the Victoria tweed circuit I fell in love with them.
They were nos GE, Phillips, Sylvania and sounded beatiful, much rounder, sweeter top end than the 12ax7 in the same amp; and they do have beautiful gain and break-up,
a beautiful blues type tube.

My disclaimer is that I liked them in THAT type tweed circuit, not in say, a Marshall type amp, didn't care for them in a Vibro-King.
But, still they are a great, great tube.