Replacement tubes for a Mesa Boogie Walkabout

[Guapo]

I've just bought a second hand Walkabout amp about 3-4 y.o. and I would like to replace the original 12AX7 tubes. I've read that the original Mesa Boogie 12AX7 tubes (Sovtek made) should have some level of microphonics. Any suggestion for good replcement tubes for this particular amp? I play upright bass, often with slap.

 

[eldave777]

Boogie tubes are usually less expensive than sovtek. Also boogie puts a 6 month guarantee on tubes. They also sell them in matched pairs and they say your amp won't need to be biased if you stick with boogie tubes.

 

[BillisCool]

Preamp tubes NEVER need to biased.


Read the reviews, pick the ones you think might suit you best.

I use JJ's and they sound excellent.

 

[Guapo]

Thanks guys. I have one more question. Do the 12AX7 have to be of the same brand? As far as I can read, they serve different purposes in the circuitry of the Walkabout. Am I wrong in saying that the one in the preamp will mostly affect the final sound?

 

[tombowlus]

The short answer is that the JJ's really are an excellent choice, and my favorite option for the Walkabout among the tubes currently in production. The longer answer can be read on my blog, but here's the relevant information for the Walkabout:

Preamp tubes in Mesa Walkabout

Some time back, I had an opportunity to run through a number of different preamp tubes in my Mesa Boogie Walkabout. The tubes at my disposal were as follows:

Mullard 12AT7/CV4024
JAN Phillips 12AX7
JAN GE 5751
Shuguang 12AX7C9
Telefunken ECC83 (smooth plate)
JJ ECC83S

The original Mesa tubes said "Russian 2" on them, but I don't know who made them.

Virtually all of the tubes mentioned above offered some kind of improvement over the stock tubes. However, most differences were very subtle.

The Mullard was by far the warmest sounding, and had a good deal of low mids - too much for the already mid-heavy Walkabout. Still, if you are looking to add some meat, the Mullard would certainly do that.

The JAN Phillips is a great all around tube. Very nicely balanced tonally, with good articulation.

The JAN GE 5751 also had good tonal balance and was a pleasant sounding tube - not harsh at all. However, with the reduced gain, it didn't overdrive as well as the others, which is something I like to do with the Walkabout.

The Shuguang was a bit of a surprise. Upon first firing it up, I thought that it might be the ticket. Very robust signal and tone, overdrives great. However, then I noticed that it was really bringing out the finger/string noise in a huge and somewhat obnoxious way. I don't know if this means that it was slightly microphonic, but it was not desirable. Too bad, because otherwise this tube has a lot of promise.

The Telefunken was the most articulate tube of the bunch, with a bit more upper mids than most. Very clean sounding tube with the Gain down and the Master up, and probably sounded the best of the bunch when overdriven. Good balance, too.

The JJ was very similar to the Tele. Not quite as articulate, but perhaps had sweeter high end. Overdrove quite well, though not as nice as the Tele.

By comparison, the stock Mesa tubes did not have as much articulation as any of the tubes above (though they were close to the Mullard in that regard), and the tone was not as coherent. They did overdrive quite nicely, though not as convincingly as the Tele or JJ. Granted, there wasn't a huge difference overall, but I would say that you can do better than the stock tubes, and it shouldn't cost you an arm and a leg.

Ultimately, it came down the JAN Phillips, the Tele, and the JJ. These three were the most similar sounding of the bunch. I ended up choosing the Tele for its articulation and best overdrive tone. The JJ would probably be my second choice, although the JAN Phillips was very, very comparable.

The Walkabout has a second tube which drives the MOSFETs, and after playing around a bit, I chose the JAN Phillips for that duty. It really is too bad that the Shuguang had that string noise thing going on, because it really kicked in the pre-MOSFET socket - most balls and gain of the bunch.

There are a lot of good tubes that I didn't get a chance to try, but there you have the results of my own very unscientific preamp tube shootout.

Hope this helps, Tom.

P.S.
I got my tubes from Doug's Tubes, and he was very helpful.

 

[Guapo]

Thanks a lot for the detailed review of the tubes! Upon that I have chosen 4 different tubes and I'm going to test them as soon as I receive them. One last question: is the preamp tube the one on the right (facing the front of the Walkabout) close to the air grille?

 

[tombowlus]

Thanks a lot for the detailed review of the tubes! Upon that I have chosen 4 different tubes and I'm going to test them as soon as I receive them. One last question: is the preamp tube the one on the right (facing the front of the Walkabout) close to the air grille?

The preamp tube is the one closest to the front panel, and the driver tube is the one closer to the middle of the amp.

Tom.

 

[Guapo]

Tom, would you go for two identical tubes or would you also consider a mix. I've read somewhere that one should choose one tube for the preamp section to achieve a particular tone and temper, while the mosfet driver tube should be more neutral. Do you agree on this?

 

[tombowlus]

Tom, would you go for two identical tubes or would you also consider a mix. I've read somewhere that one should choose one tube for the preamp section to achieve a particular tone and temper, while the mosfet driver tube should be more neutral. Do you agree on this?

I don't think that there is any need to use two identical tubes, unless those happen to be the two tubes that sound the best in their respective positions. The two tubes have different jobs to do, and therefore, it's entirely possible (if not likely) that two different types of tubes would sound the best.

 

[bassman blue]

just ordered a bunch of tubes from "Doug's Tubes," great guy, very helpful!

 

[tombowlus]

just ordered a bunch of tubes from "Doug's Tubes," great guy, very helpful!

Cool! Let us know how your experiments work out!

Tom.

 

[Guapo]

ok now I also did some tests with a bunch of tubes, some of them new, some other vintage tubes.
It hasn't been easy and still don't think I'm done with it, as there are so many different combinations of the the preamp tube and the mosfet driver tube.

The tubes I have tested are:

Groove 12AX7M (Mullard) new
JJ Tesla 12aAX7 new
TungSol 12AX7 new
Sovtek 12AX7LPS new
Electro Harmonix 12AX7
Telefunken ECC83 vintage
Mullard CV4004 vintage
Mullard ECC83 yellow label vintage

The best combination I got so far is the Mullard CV4004 with a JJ Tesla 12aAX7 in the mosfet driver slot. The CV4004 wasn't as boomy and aggressive on the lows as the Mullard ECC83, yet very clear and defined and with a massive bass. The Telefunken was perhaps the best on mids and mid-lows, but the highs were a bit too mellow for my taste.

The vintage tubes didn't come cheap. The best of the new tubes for the preamp slot would have been the Groove 12AX7M, which was close to the Mullards. Unfortunately it also produced a tic-tac sound that added an unwanted, fixed pace metronome function to the Walkabout. It must have been a bad tube.

 

[JOME77]

Glad I came upon this thread! I read a similar thread several months ago and actually printed out Tom's summary of various tubes and their sound tendencies. I planned on ordering a few to experiment with but just never got around to it. I think I'll do that now. I do have to say though that even with the stock tubes in my Walkabout I've been absolutely amazed with the sounds that I've gotten. And the fact the Mesa put it all in a 13 lb package is amazing! My Thunderfunk TFB-420 is still my main amp but I'll always keep the Mesa around for the rock gigs! Such a huge warm sound!

 

[Guapo]

Joe, the Walkabout can sound better with other tubes but the standard Mesa ones, which I believe are some sort of Sovtek. Russian preamp tubes generally are not bad, but it seems like they weight more gain than sound quality. I find the sound of the standard valves a bit muddy and unfocused. If you like a massive deep bass then get a Mullard or even the Groove replica - hopefully these 12AX7M are not all of them bad, as mine was. If you like a more sober, cultivated and complex sound with many details, the Telefunken would probably be the one for you.

When I started reading about preamp tubes I just could not believe that a 40 years old tube could sound better than a modern one ... but I realized, it's actually true.