Supa-muddy tone - tubes, yes?

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Jackie

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Just trying to confirm this (hope it's the right section):

My TriAxis/2:90 has suddenly turned super muddy. Like, "Presence to 3 o'clock and still undefined" muddy (previously had it set to below half, always, even with my darkest guitar).

Side note - I tried plugging the TriAxis into my JVM to see if it's the preamp's fault and nope, it wasn't.

Anyway, the tubes in that thing are old... yet the seller claimed he had retubed it a couple of years before selling it to me and that he didn't use them at all, but to me they look about as old as Mother Earth! I mean, they're a MESA tube that isn't even in production anymore (STR-415 I think).

So - can older than Jesus tubes cause such a sudden muddyness? Should I try swapping the 12AX7s to see if they are making this (though I doubt it since it's just a driver and 2 PIs)?
 
The 2:90 also has 3 internal 12AX7's right? It could be that very much. If you have STR-415's they are rated for 10,000+ hours, I doubt that would be it. Now if it's the STR-430's (Sovtek/EH) that might have come factory in an early 90's 2:90, it could very well be worn out power tubes, I barely put 300 hours on those before they went.
 
Thanks for your answers guys.

dodger, I didn't like how they sounded to begin with (too "squishy" for me) but I don't really think it's fair to judge them in this kind of state. Would be nice if they would be in pristine condition :mrgreen:

Sonic, I think those tubes are seriously old, like 10+ years so I think that if not anything else, they are mechanically screwed. I can literally hear them rattle on the inside when I power up the amp...

I'll try swapping the 12AX7s (though I cringe at the thought of that, y'know, taking the thing apart, out of the rack etc.) and see what happens.

Anyhow, just for the record I'm planning on dropping in an octet of =C= 6L6s... they seem like a good choice. What d'yall think? I like how clear and punchy and "strong" the =C= tubes sound...
 
Jackie said:
Thanks for your answers guys.

dodger, I didn't like how they sounded to begin with (too "squishy" for me) but I don't really think it's fair to judge them in this kind of state. Would be nice if they would be in pristine condition :mrgreen:

Sonic, I think those tubes are seriously old, like 10+ years so I think that if not anything else, they are mechanically screwed. I can literally hear them rattle on the inside when I power up the amp...

I'll try swapping the 12AX7s (though I cringe at the thought of that, y'know, taking the thing apart, out of the rack etc.) and see what happens.

Anyhow, just for the record I'm planning on dropping in an octet of =C= 6L6s... they seem like a good choice. What d'yall think? I like how clear and punchy and "strong" the =C= tubes sound...
IMO, =C=s are a very good choice. They are my favorites after STR415s (pre-Mark IV) or STR420s (Mark IV).
 
dodger916 said:
Jackie said:
Thanks for your answers guys.

dodger, I didn't like how they sounded to begin with (too "squishy" for me) but I don't really think it's fair to judge them in this kind of state. Would be nice if they would be in pristine condition :mrgreen:

Sonic, I think those tubes are seriously old, like 10+ years so I think that if not anything else, they are mechanically screwed. I can literally hear them rattle on the inside when I power up the amp...

I'll try swapping the 12AX7s (though I cringe at the thought of that, y'know, taking the thing apart, out of the rack etc.) and see what happens.

Anyhow, just for the record I'm planning on dropping in an octet of =C= 6L6s... they seem like a good choice. What d'yall think? I like how clear and punchy and "strong" the =C= tubes sound...
IMO, =C=s are a very good choice. They are my favorites after STR415s (pre-Mark IV) or STR420s (Mark IV).
I loved the 420s in my old dual recto
 
Well I rechecked the tubes and they are STR-420, not 415.

They are completely screwed, yes. Definitely need to retube. They're all brown inside and one of them is actually loose from it's base so much you can move the glass part without moving the base!! :?

What are the roles of the three 12AX7s inside the amp? Since I'm at it I'm gonna change those too. Any suggestions to go with the =C='s that I'll stick
I HATE not being able to play my Boogie rig. I love playing my Marshall and all but the Boogie has it's own magic that's very easy to succumb to and I really miss that menacing and "no-matter what I do with it it stays clear" Mark IIC+ mode growl, that throat-slashing, window-shattering recto WROAR and that crystal clear Mark IV clean.
 
Jackie said:
What are the roles of the three 12AX7s inside the amp?

Driver tubes. I think the one is to balance the voltage going to each channel, while the other two are to balance the voltage going to each pair of tubes in each channel.

Or, I could be totally out to lunch on how a driver tube functions...
 
No PI? :?
I was under the impression that a poweramp needs a phase inverter...

How would using different preamp tubes affect the tone/feel? Totally? Not much? "String brand change" difference?
 
Jackie said:
No PI? :?
I was under the impression that a poweramp needs a phase inverter...

How would using different preamp tubes affect the tone/feel? Totally? Not much? "String brand change" difference?
It sounds like the 12AX7's are the phase inverters, which are also (and maybe more accurately) called "drivers". That's what screamingdaisy called them, so I assume that's what he meant.

PIs influence tone in a global way similar to the first input tube (typically the V1 slot). The influence is not as great, but it's close, and it is global. Preamp tubes do more to shape tone than drivers as they are in the tone and gain-generating circuits. The earlier in the chain, the more influence.
 
Jackie said:
No PI? :?
I was under the impression that a poweramp needs a phase inverter...

I checked the 2:90 manual and couldn't find a tube assignment, however my 2:100 manual lists all three as being drivers.
 
Oh, thanks for that explanation.

I think I'm gonna go with a TungSol or EH. Thanks for all the info guys!
 
FWIW, the PI or "driver" tubes are the hardest working preamp tubes in a push pull power section amp. Good to replace also when the power tubes get old enough to need replacing. 2/90 is a push pull design, like most guitar amps.
 
212Mavguy said:
FWIW, the PI or "driver" tubes are the hardest working preamp tubes in a push pull power section amp. Good to replace also when the power tubes get old enough to need replacing. 2/90 is a push pull design, like most guitar amps.
+1
I would think that one of those 12AX7's is an input buffer of sorts. The other two would be PI's, one tube for each stereo side ( 1/2 tube for each pair of powertubes).

You could call Mesa to be sure.

Dom
 
Talked with my tech on the phone and we had a little discussion on tubes (I love it how we like the same things in tone so talking with him is easy).

I asked him if there was a cheaper alternative to =C='s and he recommended TungSol, I'll probably get the =C=s anyway but if I'm unable to muster up the money at least I have an alternative.

Then I asked him about the 3 12AX7s in the 2:90 and he said that two are indeed PI's and one of them is an input buffer (each half buffers one poweramp channel), so I know what that does (nice one Dom! :mrgreen: )
I also asked him in a BTW manner if it's worth mixing EL34s and 6L6s and he said "nope, at least not in the rack poweramps and without a bias pot", but he did give the older Mark series props for their bias setting for mixed tube operation and said he would have no second thoughts about using EL34+6L6 in a older Mark amp.

Anyway, interestingly enough, he recommended JJs (though neither of us are a fan) and/or TungSol (I'm not a fan, at least not in Marshalls).
He also recommended that combination for my TriAxis - it's tubes are working fine but I told my tech I have a feeling I could do better and as if he was reading my mind he said "Yeah those tend to sound a bit dark and lifeless/boring" which is exactly how I feel.
I hear that JJs are pretty gainy/compressed preamp tubes, and in my experience they turned out that way too. That was in my Marshall though. I like my tone to respond to my playing and I don't want to lose that.

Anyone have any experience with the JJ/TungSol combination?
I doubt it would be good to slam 5 JJ's in the TriAxis :?
 
Well someone must really hate me. I swapped all 8 of my cruddy tubes for 8 shiny =C= 6L6s and there is 0 change :evil:

It's like the Presence knob doesn't work. I dime it or leave it at 0, the difference is like moving the knob for about 2 "o'clock" settings" when the amp worked normally.

I'll swap the 3 12AX7s and if that doesn't help I'll just sell the **** thing.
 
I swapped the three inside 12AX7s with 2xTungSol and 1xJJ and finally the sound I was used to came back.

My only question is how the tubes are laid out - I understand there's one driver tube and 2 PIs, one for each channel.

If you're facing the preamp, I'd say they're (lets call them TUBE#)

TUBE1 (PI) TUBE2 (PI) TUBE3 (Driver)

since TUBE3 is closest to the input... so I put the JJ in the TUBE3 slot and TungSols in the other two - did I use the TungSols in the PI slot and JJ in the driver?
 
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