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JJ's 12ax7 + Trace Elliot RAH350SMX = WOW!

Kelly Lee

Kelly Lee

Yeah, I'm a guy!
Supporting Member
Feb 17, 2004
6,317
29
Marana, AZ, USA
www.actshooters.com
#1
I just thought I would share my experience. I recently decided to try a JJ 12ax7 in my QuatraValve and thought "hmm, why not try it in my RAH350SMX head as well?" I have read so many places that a preamp tube swap on a hybrid head really doesn't make much of a difference.

Well, I disagree when it comes to TE heads! WOW, what a difference one little tube can make! My tone became much thicker and more round. It also fattened up the bottom end alot. One other little side note, my already excellent sounding harmonics somehow sound even richer. Wow, what else can I say? :bassist:

Any other Trace Elliot or other hybrid owners done a tube swap with noticeable improvements?
 
#4
How did you like it in your Quatra Valve? I really think that the JJ is the best modern 12AX7 out there. In many ways, it reminds me of my NOS Telefunkens. Great tube. I still am trying to find the time to go through all my NOS tubes and pick the ideal set for my V8 and Quatra Valve, but you can do a lot worse than just going with all JJ's let me tell you what!

Tom.
 
#5
I put 4 new JJ's in my Mesa 400+ and it definitely made a big difference. Bob @ Eurotubes will 'pick' tubes to match your tonal goals too...a nice service to have when people these days don't know so much about tubes.

He tells me that the biggest difference will be when he gets his hands on the power section of my 400+.
 
#6
I put 12ax7's from a 1960's stereo into a SWR 350x and aPresonus TubePre preamp. There was a noticable difference in both units although the preamp had more of a difference. The tubes were Telefunkens, manufactured for Harmon Kardon. They had less than 50 hours of use ( maybe less: my parents hi-fi system) and were dormant for 30 years. I have the feeling that tubes, like basses, have their own mojo, and it differs a little from tube to tube, even with identical make and manufacture.
 
#7
I want to echo Burning Skies comments about Bob at Eurotubes. I've worked with him a couple of times now. He wnet waaay out of his way to help me thru my last project. He's an exemplary vendor, and I will do biz with him again in the future.
I may have to buy a few more jj 12ax7's to play with in a couple swr/eden this's and that's I have laying around....

It's 110 dregees here today.
Playing with tubes in the basement sounds like a really good idea;)
 
#9
43% burnt said:
Cool, I'm gonna try this with my trace too. I've also heard nothin but good stuff about JJ tesla's. Is there any biasing that needs to be done, or Can I just pop a new one in my AH250?
Click to expand...

You don't need to bias preamp tubes. As long as it is the same tube type, you should be plug and play friendly! Some preamps will even allow you to try different tubes with the same pinouts (like 12AX7, 12AU7, 12AT7), but inquire as to this compatibility before you do.
 
#10
tombowlus said:
How did you like it in your Quatra Valve? I really think that the JJ is the best modern 12AX7 out there. In many ways, it reminds me of my NOS Telefunkens. Great tube. I still am trying to find the time to go through all my NOS tubes and pick the ideal set for my V8 and Quatra Valve, but you can do a lot worse than just going with all JJ's let me tell you what!

Tom.
Click to expand...

Tom, I actually haven't tried it in the Quatra yet. It sounds so good in my SMX I don't want to pull it out! :p Ah, I'll probably try it out after band practice tomorrow. I'll post back when I do.
 
#11
Kelly Lee said:
I have read so many places that a preamp tube swap on a hybrid head really doesn't make much of a difference.
Click to expand...

Where the heck did you read that??? Believe me, mys XS800H sounded great with the stock Sovtek 12AX7, but putting in a Groove Tubes ECC83S in it's place I got very similar results to yours.

From the info page for GT ECC83s: GT-ECC83-S
(European, very linear, or true, tone...might be best bet for bass). The standard tube of Marshall and Vox amps.

I agree, the ECC83S might just be..."best bet for bass!"
 
#12
Kelly Lee said:
I don't really know what tube was in there. It has absolutely no markings on it. It looks just like the JJ I put in. Everything is identical except for the lack of markings and the obvious tone differences.

Here is a pic of the JJ:
Link Removed
Click to expand...

This is my favorite tube for my SWR SM-400 and SM-400S! Glad to hear they're gaining in popularity. The short plates (is that the right term??) in this design make it easy to ID. Amost every other tube I've seen has longer plates.

On the SWR amps, the tube makes a difference. OTOH, different tubes on the Eden WT-300 I owned for awhile made no difference.
 
#13
I swapped out tubes in three different SWR heads... In the Chrome 350 (not 350X) I had, it made no difference at all what I put in there.

In the SM-400S and the older, red-faced 350 it did make a difference. More so in the 400S.

Noticeable differences were also noted in a couple of Hartkes (a 3500 and a 7000). The biggest difference I noted in preamp tube swapping came with an Ampeg SVP-Pro I had. Tubes used were NOS Chinese in the SVP, and assorted Svetlana, JJ's, and GT's I've had laying around...
 
#14
tornadobass said:
On the SWR amps, the tube makes a difference. OTOH, different tubes on the Eden WT-300 I owned for awhile made no difference.
Click to expand...

Of all the gear that I have tried swapping tubes in, I heard the least difference from my Eden Navigator. I think it has to do with the way that Eden incorporates the tube into their preamp layout.

Tom.
 
#17
Microbass said:
these are going pretty cheap on ebay. i may have to pick one up!

are there specific types of these? or are the JJ 12AX7's all the same? (i.e. MIA, MIM etc?) :)
Click to expand...
I think they are actually all the same but I too recommend Bob at [Invalid or Expired Link Removed]. He has been very helpful and has put up with my many e-mails.

He is selling the standard tube for $8 and he has the high gain version version for $10. They are the same tube its just that he test them for output to make make sure they gain is really good. Check him out.
 

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