5751 preamp tube

[ssgfowler]

After hearing all the glowing reviews of these little bottles, I broke down and ordered a JAN NOS Phillips.

Man, Cgil and all others were right.

I A/b'd it with a drawerful if 12AX7's and I like it best.

My Marshall modded jr. has no clean headroom whatsoever, and I like it like that, but that little preamp tube gives it just the warmth I was looking for and still keeps the power tube singing.

I'm gonna order another just to keep for when this one dies.

[m-theory]

Some like that tube, others don't. I've personally ever tried one, but a buddy of mine can't stand them. Go figure...just like always, tone is subjective! Good to hear that it worked out for you!

[TWANG]

I bought one since gil said it was a good choice. and It's my fave, now, too.

I gotta get me another few..

 

TWANG

[fenrirlupus]

70% power of the 12ax7... i guess if i ever need to quiet down an amp...

is it brighter/darker than a 12ax7? (compare to the chinese one i guess, that one seems to be a pretty standard tube in new amps w/ 12ax7's...)

[m-theory]

70% power of the 12ax7

This is what's really goofy...trying to assign percentage values to these things is just nonsense. My amp tech buddy buys 12ax7s in hundred lots, and, with his equipment, he'll find gain ratings of anywhere from 50 to 120 or so. How can a 5751 be 70% of the gain of a 12ax7, when 12ax7's can rate almost anywhere? What is that 70% figure based upon?

 

They're not about quieting down an amp, though. They're about reducing front end gain, which can also be accomplished by using low gain 12ax7s as well.

[51xt33]

So if I understand this correctly, does this mean that using the 5751 should give some higher clean headroom and yet maintain the same volume as the 12AX7?

[m-theory]

If there were such thing as standardized tests for gain, and if there were such thing as consistency amongst tubes, you could say that, but when neither are the case, it's really just an arbitrary comment, isn't it?

 

If you happen to get a 5751 that's actually lower in gain than whatever 12ax7 you're currently using, yes, it will reduce gain a bit.

 

However, you could also be just as likely to find the 5751 to be of HIGHER gain than the 12ax7 you're replacing, given the vast range of gains in today's new production tubes.

[TWANG]

I think he's right!

I know that the 5751 I have varys in it's comparison to different 12ax7s I have.

 

it's ok for this stuff generally, I think. that is, a 5751 SHOULD be more headroom.... and that's how it works out comparing my

westinghouse to the jj.

 

But the 12AT7 seems exactly like the 12AX7...

yet they all have a different sound especially in the overdrive.

 

on the other hand. it sure is fun to try them out and it's fairly cheap.

so.. why not?

 

TWANG

[cGil]

Yep. Great fun sampling tube tones. Hey, ya need spare tubes anyway, right? And you can have extra fun from just having a variety of 'em to try.

 

Gil...

[Steven Lister]

...and for those who don't already know:

--- some valve sellers let you specify on your order if you want low/high gain (some even by gain #)?

 

As m-theory pointed out the gain tests are not standardized. But if the seller is testing all valves the same way on the same equipment then they have a benchmark # and can tell you from their stock and tests what is low/high so that you can select whatever suits your needs. Or you can buy a bunch and spend your Saturdays swapping for tone.

 

Hit every BLUE NOTE baaaby..., I'm going to play on:-"

[Bakz]

The first time I used a 5751 was back in the late 70s. I've always used the milspec ones, they are designed for radio and comm circuits. If you are looking for a SRV sound, you've got to have at least one channel loaded with these in your front end circuit. My favorite in a VJr is a Sylvania 12AX7-R (only have one that somebody gave me), I get a real vintage gain from this. But a 5751 is thicker and will most definitely move your sweet spot clockwise, much more so than a 12AT7. I run a 5751 in one VJr Head (I call it Texas), and the 12AX7R in the other. Both have had some gain mods. Got lucky and purchased a half dozen US 70s made GE 5751s about 6 years ago before people figured out what they'd do. Lucky for us, preamp tubes have such good life.