Which Tubes Replace 12AX7 for LESS Gain in my 5.25

A question about tweaking my tone.......involving tubes and gain.

I would like to have LESS gain in the preamp, so that the pre-gain control can be turned up more before the sound starts to distort. I dont really like distortion, I would much rather go for clean sustain.

Which tubes can I use to replace the 12AX7's so that I get LESS preamp gain that is still clean and smooth, not too bright or edgy, etc.?

Right now I'm using standard Tung-Sol 12AX7's, but I'm willing to try 12AU7 or 12AT7 if that will work with the 5.25 Express. Name some brands if you like, but I wanna make sure I'm using lower gain tubes that are ok and safe to use with this amp, and in what sockets/positions to use them. I just wanna make sure I am going for substitutions that will help the amp, not hurt it.

I just got a new matched pair of JJ EL84's from Doug's to experiment with, but it's that fizzy buzzy preamp distortion that I want to try and minimize. I really like what happens if I turn the gain off, turn the master volume waaaay up, then bring the gain back up slowly. But when the fizzy kicks in, that's when I start to frown.

THANKS for your suggestsions!
Gary

Here:
http://thetubestore.com/gainfactor.html
Any and all of these subs should be safe. With a combo, it's easier (for me, anyway) to place the amp upside down on a table, even removing the speaker grille and speaker for a nice big, round hole to reach through.
Hope this helps

MrMarkIII said:

Here:
http://thetubestore.com/gainfactor.html
Any and all of these subs should be safe. With a combo, it's easier (for me, anyway) to place the amp upside down on a table, even removing the speaker grille and speaker for a nice big, round hole to reach through.
Hope this helps

Click to expand...

CoooL! Great info in a compact space there.

Do I need to downsize ALL of the preamp tubes? Or, as the manual might imply (but does not say), do I only need to put lower gain tubes in the 1st gain stage sockets? It appears each of the two channels has its own first gain stage tube.

I suppose I could experiment with all of them, but if just doing the first gain tube in each channel will get me 90% of what I want, then that would be great.

A 12AT7 will have about 60% gain of the 12AX7 but will have *more* current flow. I like a 5751 in V1. 70% gain of 12AX7 but less current flow. The NOS JAN Phillips versions are readily available and affordable. They tame the gain, have decent tone, and when the gain is cranked still have good distortion.

ty

I was just looking at Doug's and wondering if the Jans would be in stock and ready to ship. I may try one of each, 5751, AT7, and an AY7.......mix and match pairs in V1 and V2 and see if I get closer to what I hear in my head.

Why are the 5751's more expensive than the other variants? Double, usually.....

Microphonics won't be an issue with these black plate or grey plate tubes? I may end up trying to run my master vol full on, and I used to get nasty microphonic feedback when I did that with black plate Sylvanias in the Subway Rocket.

soundchaser59 said:

CoooL! Great info in a compact space there.

Do I need to downsize ALL of the preamp tubes? Or, as the manual might imply (but does not say), do I only need to put lower gain tubes in the 1st gain stage sockets? It appears each of the two channels has its own first gain stage tube.

I suppose I could experiment with all of them, but if just doing the first gain tube in each channel will get me 90% of what I want, then that would be great.

Click to expand...

It's always best to do one tube at a time, then use your ears. With the Express, start with V2, not V1. V2 is the first gain stage (although there is lots of overlap). There's a tube task chart at the end of the manual.
The 5751s could be NOS, thus more pricey. But you should definitely try one if possible, they have a nice "woody" sound to my ears.

Yeah, it's more time consuming, but changing one tube at a time is the proper way to do this experiment......

Darn it, now I'm gonna have to spend even MORE time playing my guitar! Shucks..... :shock: :lol: 8)

I'm still waiting for a reply from Frenzel, I'm gonna do this same experiment in the 5E3.

I'm trying to mimic that Duane Allman / Dicky Betts super clean sustain like a bell lead sound, sorta like what they had in Ramblin Man or Sweet Melissa or Revival.

soundchaser59 said:

I'm trying to mimic that Duane Allman / Dicky Betts super clean sustain like a bell lead sound, sorta like what they had in Ramblin Man or Sweet Melissa or Revival.

Click to expand...

Hmmm... You may need EL-34s and Greenbacks for that sound.
Or, with an Express, start with the Crunch mode. That's about as close to a non-master Marshall as you're going to get. Back off the guitar volume for clean, turn it up for lead. That's what they did.
Speaking of, um, speakers, changing speakers may get you a larger tone change than tubes.

MrMarkIII said:

soundchaser59 said:

I'm trying to mimic that Duane Allman / Dicky Betts super clean sustain like a bell lead sound, sorta like what they had in Ramblin Man or Sweet Melissa or Revival.

Click to expand...

Hmmm... You may need EL-34s and Greenbacks for that sound.
Or, with an Express, start with the Crunch mode. That's about as close to a non-master Marshall as you're going to get. Back off the guitar volume for clean, turn it up for lead. That's what they did.
Speaking of, um, speakers, changing speakers may get you a larger tone change than tubes.

Click to expand...

Yup, I've spent the last 4 years cycling thru 4 dozen different speakers. I've already pretty much completed the speaker quest aspect of this tone chase. I'm settled on the EV's (10, 12, and 15) and the Weber ceramic Michigan. Everything else has come and gone and been sold and shipped.

This experiment is not so much about the subtleties of the tone itself, as it is about taming the behaviour of the amp and it's gain path. Seems like most amps these days are designed by the axiom "Just max out everything, then anything goes." Well, I dont want to just blindly max out everything. I'd like to have some of my own say about how my amp handles the gain stages. I dont want full throttle gain at every turn. I believe that's where the fizzy buzzy crap that I dont like comes from. I wracked my brain trying to get away from that with the solid state marvels. Now it's tube time!

The Frenzel 5E3 is running EL34's. I challenged myself a few days ago to just skip the pedal board and run straight into the amp and see what I could get out of it. I love the sound with the master on full, but the preamp distortion kicks in too early for my taste. So the tube filament in my head came on and I started thinking about controlling preamp gain. If I could get that gain knob up to 50% with the master still on full, I think this thing will start to really sing......just like that Subway Rocket used to.

Then, of course, I had the brilliant idea to do the same therapeutic massage with the Express!

And now I'm hearing that using lower gain tubes will make them burn up quicker? And maybe have smoother distortion at lower volumes instead of more clean headroom?

Blind me with science......

Well, I have an AT7 and a 5751. I tried switching them both between V1 and V2.

It sounds best (other than the standard 12AX7 configuration) with the 5751 in V2. I notice it will tend to break up earlier, given the same gain settings. But it is also a tad bit quieter or softer. Not much, but noticeable. Also noted that the early breakup was not smoother sounding to me, but sounded more gritty and more fizzy. Not bad, just not as good as before.

Overall, I think this Express sounds best with the regular 12AX7 compliment in it. But I got the tubes from Doug's Tubes, and he told me the 12AX7EH he sent me would have smoother highs and smoother upper mids. I was skeptical, but he was right. Again it is not a glaring difference, but it is noticeable, enough to make me respect his advice on tubes. I'm thinking about changing out the JJ EL84's now too.

As a side note, where this 5751 and this 12AX7EH really made a cool and sweet difference is in the Frenzel 5E3 clone. That amp really made the differences among the tubes much more obvious, and it was like ear candy with the 5751, the EH, and the master on full with the vintage Strat pickups. WOW! As if that isn't cool enough, it is obvious that the Frenzel and the Barber Tone Press are a match made in heaven.

Glad I did this, everyone should try it. This is a whole different tone quest than the speaker chase I was on.

My earlier trials I used only one lower gain tube at a time.

Tonight I tried something and "accidentally" got a great tone, and also got rid of some of that piercing high freq icepick noise coming from this high efficiency EV speaker.

I put a JAN 12AT7WC black plate in V2 (60% gain in stage 1) and the 5751 in V1 (70% gain in stage 2) and it sounds just as awesome as ever. The only difference is I can only turn the burn channel up to 50% on the master before it will start to give me too much feedback. I can still turn the clean channel up to 100% master volume with all pedals engaged and it sounds GREAT! And the burn channel at 50% master is still louder than the clean channel at 100% master.

Me thinks this will work out pretty darn sweet after all.

Anybody know what happens if I vary the gain of the tube in V4 (phase inverter)?? My Express came from the store with an ECC82 in that slot, which is supposedly only about 20% gain? What happens if higher gain tubes are used in V4?

I believe the ecc82 is the same as 12at7, whereas the ecc81 would be the 20% gain or equal to 12au7...a higher gain PI tube will push your power tubes a bit harder, getting more breakup earlier.

your tube choices for V1 and V2 are what I use in my Pignose G40 and G60 combos and give killer tone as you describe. The gain controls and tone controls are much more responsive

ty

thunda1216 said:

I believe the ecc82 is the same as 12at7, whereas the ecc81 would be the 20% gain or equal to 12au7...

Click to expand...

Here is a good starting reference.....

http://thetubestore.com/gainfactor.html


everything I've seen so far equates the ECC82 with the 12AU7. The differences are kinda subtle to the untrained non-musician ear, but to us six-shooters it is noticeable.

If you are trying to get Duane Allman's tone, and you want smoother/less "fizzy" gain, you might find that putting down the Strat and picking up a Les Paul like he used, or even an SG, with PAF Humbuckers is all you need. Single coils are brighter, thinner, and sound a lot different than PAF humbuckers. Single coils in the Strat are made for more trebly, biting response, where PAF's are smoother, thicker sounding, with less higher top end. Also, putting JJ's power tubes in a fixed bias Mesa is a mistake. JJ's are all over the place, and should be used in amps where you can adjust bias/balance. Mesa's cost more, but will always be in perfect range for a mesa. On the other hand, JJ 12AX7's are identical to Mesa 12AX7's and make an excellent replacement. The reason most amps these days are adjustable bias, is because tubes are not made to the precise specs that they once were. Mesa gets their tubes from the same place as many others, but passes over the ones that don't test out to their exacting specs. This is more costly, but pays off in reliability and not needing to have a tech bias your amp every tube change. Buying a matched set of JJ's doesn't help anything except the need to balance, but they still won't be correctly biased to match your amp, as are Mesa's.
Also, try the reverse of your method on preamp experimentation. Keep the ax7's but try putting an aT7 in the PI/driver slot(V4 on yours, i think). Then try putting one in V3, etc, if need be. Odds are you'll have what you want and stop at swapping the PI out for a aT7. That way you might keep from thinning your tone as much. I like an AT7 in the PI. You might also try a "safe mismatch" on spkr ohms. Put the plug from your 8ohm spkr into the 4ohm jack on the amp. It gives a bit "spongier" response. I do that with my 5:50. Its safe to do that with a Mesa OT. You'll also likely never hear exactly what you want from single coils, if you are aiming for Allman's tone. You may even find that humbuckers give you what you want toward that tone without swapping anything in the amp and sticking with all aX7's in the preamp and PI. Nothing against single coils... I prefer them- its just not what DA used and makes a different sort of sound.

You could always call Doug at Dougs tubes.

Tell him what you're trying to do, what tone you're trying to get and such. Follow his advice.

There's several of us here who are rocking Dougs tubes in our Mesas. I love what he did for both my amps.

YMMV!