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2:90 12ax7's?

Posted: Tue Oct 09, 2018 6:26 am
by Squidz66
Hey all,
I have been away from "TBB" for a while..But as all ...We finally come back
I have one question about the 12AX7's in the 2:90...???

What does anyone suggest?

I hear that we need balanced..and I hear that balanced is a load of BS..

Do the PI need to be balanced?

Will any particular tube make a difference?

I have some new Mullards 12ax7 and 4004 and some Elecro harmonix ...

Any suggestions would be helpful



Thanks

Re: 2:90 12ax7's?

Posted: Tue Oct 09, 2018 12:08 pm
by jediguitarist
Not sure how similar the guts of a 2:90 are compared to a 295, but I've thrown in what ever 12ax7s I've had into it.

I picked up a used 295 back in 01' or 02' which didn't have any 12ax7s in it. I had a pair of Mesa branded ones and pair of Groove Tubes and put them in. I didn't even bother to check the socket assignments. The 295 is symmetrical in it's physical layout so I mirrored one side to match the other. It worked and I haven't changed out those tubes since.

I have two 295s and they sound pretty similar. One having all Mesa branded and the other has a mash of Mesa, Groove, Tesla and GE. The all Mesa power amp have the exact same 12ax7 in all four slots.

Like I said, I'm not familiar with the 2:90 but I would think it would accept any 12ax7. I'd really like to hear those Mullards, though. :mrgreen:

Re: 2:90 12ax7's?

Posted: Sun Oct 14, 2018 5:38 am
by Squidz66
jediguitarist wrote:Not sure how similar the guts of a 2:90 are compared to a 295, but I've thrown in what ever 12ax7s I've had into it.

I picked up a used 295 back in 01' or 02' which didn't have any 12ax7s in it. I had a pair of Mesa branded ones and pair of Groove Tubes and put them in. I didn't even bother to check the socket assignments. The 295 is symmetrical in it's physical layout so I mirrored one side to match the other. It worked and I haven't changed out those tubes since.

I have two 295s and they sound pretty similar. One having all Mesa branded and the other has a mash of Mesa, Groove, Tesla and GE. The all Mesa power amp have the exact same 12ax7 in all four slots.

Like I said, I'm not familiar with the 2:90 but I would think it would accept any 12ax7. I'd really like to hear those Mullards, though. :mrgreen:

Thanks Jedi,
After posting this I did see there was a few questions asking the same thing..

I have only recently purchased it ..And it sounds great.

So what I did was ..

Take it out of it's rack , unscrew the top,
See that they are MESA tubes in there
1 was a 12ax7a ...the other two were 12ax7..
Got scared!
Put them back in ..
Re-screwed and put it back in rack!!!

WEAK!!!!

I know nothing about why one would be an 'A' ...and the others not!

It is IMPOSSIBLE to actually roll these tubes...

I will have another go soon...

Is there a difference???????

Re: 2:90 12ax7's?

Posted: Sun Oct 14, 2018 5:49 am
by Squidz66
I actually meant I purchased it second hand..
Is a blue light and has a mixture of GT, Ruby, Svetlana 6L6's in it..

Its a bit noisy..

Re: 2:90 12ax7's?

Posted: Sun Oct 14, 2018 9:30 am
by jediguitarist
Most likely, the 12ax7-a is V1
While the other two are for the PI

V1 is located nearest the input jacks on left of the rear panel.
V1a - (left tube) is the Input Stage for Channel A.
V1b - (left tube) is the Input stage for Channel B.
V2 - (center tube) is the Phase Inverter for Channel B.
V3 - (right tube) is the Phase Inverter for Channel A.

I can't really say if it will make an audible difference.

I got this info from this link.
https://mesaboogie.zendesk.com/hc/en-us ... 0-I-vs-II-

You might want to check which version you have, as the Class A and Class AB sections are different in each revision of the power amp.

Re: 2:90 12ax7's?

Posted: Fri Oct 19, 2018 7:49 pm
by MesaMad1378
Hi there,
I’ve got Electro Harmonix in mine at the moment, have tried Mesa Chinese and Russians in it as well as the SPAX7’s. the only thing that really changes a bit is the noise level just slightly. Any 12ax7 can go in any place. 2 volume levels to compensate so it doesn’t really matter about balanced.