Anybody try Swapping 12AX7's for the premium SPAX7A's???

[pcos]

Mesa/Boogie has recently put a new Tube-Guide on their web site:

http://www.mesaboogie.com/Product_Info/TubeReference/TubeRefGuide-06.pdf

This document talks about the SPAX7A's as a 'premium' tube:

Our SPAX7 preamp tubes are a premium grade substitute for any 12AX7 positions - They are a “Special Requirement Preamp Tube” that possess an even higher standard of overall performance, due to their incredibly low sensitivity to microphonic noise - This is the ultimate preamp tube to use in all critical gain stage positions - It is the absolute best of the best!

I think they go for something like $5 more a tube.

So - My Question: Has anybody swapped their 12AX7's out and given these a test run? How does the sound change? I have a Lonestar Special and I would especially interested in anyone who has done this for the LSS.

Thanks!

 

[mesa jedd]

Mesa jedd from down under,No,i havnt used on lone star but i used them alot
in triaxis ,very quiet (good to have atleast one in position closest to iput),and heaps more compessed gain,which wasnt always good ,but good to have one in the chain ,and some regular ones for the rest.
Also if you have a channel you want to change use in that psition.
cheers jedd

 

[jbird]

They're what I've always used, on the recommendation of my local Mesa dealer. I believe it's what comes stock! Correct?

 

[Russ]

You might want to read my post about Mesa tubes. I tested some and wasn't pleased. This isn't to say that they don't sound good but I would expect more out of a so-called spec'd tube. The SPAX7 has an ok sound. It is not that of a Mullard or RCA. It is not that of a Telefunken or Amperex either. It is not even a Sylvania or a Phillips. I wouldn't call it a Tesla or a Tungsram either. It is obviously a new production tube that is of Russian design probably on the lines of a Sovtek WA/WB/maybe a WC screened for microphonics then wrapped in heatshrink tubing. The tube itself seems rather sterile. I have other newer production tubes that sound better that cost less (GT). I certainly have older tubes that have classic sounds that without words leave the SPAX7 sounding sterile. Yes, it can have gain but that is about the only thing you will get out of it. In fact the gain isn't even that great either. I would rather have an older tube that has the gain and the tone. The batch I tested weren't even consistent in transconductance much less anywhere near matched across the individual tube.

 

[pcos]

Russ,

Thanks for your detailed response. I will look for the other post you reference.

I ended up putting a SPAX7 in V1 of a Lonestar Special to diagnose a problem I was having with my drive channel - the local Guitar center was out of 12AX7s and the SPAX7 was all they had on hand.

This solved my problem and improved the sound of the drive channel - but I think this is more of a case replacing a bad tube with a better tube.

This is a new amp that I just bought (my first tube amp as a matter of fact) so I was sticking with the mesa/boogie tubes for now (thinking of the 5 year warentee and all) but I am intrigued - I'll have to look into trying a set of JJs or one of the other brands that folks have been having good luck with.

Thnaks again for your response!

 

[Kung-Fool]

I'm fairly certain the SPAX7 is the same as the regular Mesa 12AX7 which is just a re-labled Sovtek/EH. It just supposedly goes through extra screening for noise and microphonics.

 

[Russ]

Unfortunately they don't care much about the matching or the actual transconductance value of them other than if they work or not. I tested a bunch and found that while one side may test new that the other typically won't. I think out of a half dozen I got one decent one that still was not near matched at all. I know Mesa doesn't require matched tubes but why start off with a tube that is only half new? The other not so new side will only fail sooner than the newer side. The SPAX7 has a groovy heatshrink tubing on it. I think this is the only extra measure taken with these tubes being that they are already selected as nonmicrophonic just to get the Mesa label.

 

[Boogiebabies]

I'm fairly certain the SPAX7 is the same as the regular Mesa 12AX7 which is just a re-labled Sovtek/EH. It just supposedly goes through extra screening for noise and microphonics.

Bingo.

 

[Boogiebabies]

Unfortunately they don't care much about the matching or the actual transconductance value of them other than if they work or not. I tested a bunch and found that while one side may test new that the other typically won't. I think out of a half dozen I got one decent one that still was not near matched at all. I know Mesa doesn't require matched tubes but why start off with a tube that is only half new? The other not so new side will only fail sooner than the newer side. The SPAX7 has a groovy heatshrink tubing on it. I think this is the only extra measure taken with these tubes being that they are already selected as nonmicrophonic just to get the Mesa label.

Bingo.

You take this chance with every new production tube. I had dozens of GT 12AX7M's test 110/110 and go microphonic in a week. I still like them over any common production tube on the market for the V1 and V5. The rest are the Ruby 12AX7C9. These have great smooth tone and last for years. Out of the 50 I have in use, I have ony had two go down on me.
Other than that I love NOS RFT's and Mullards. Nothing swirls like certain NOS, or lasts 12,000 hours either.

 

[Kung-Fool]

Bingo.

You take this chance with every new production tube. I had dozens of GT 12AX7M's test 110/110 and go microphonic in a week. I still like them over any common production tube on the market for the V1 and V5. The rest are the Ruby 12AX7C9. These have great smooth tone and last for years. Out of the 50 I have in use, I have ony had two go down on me.
Other than that I love NOS RFT's and Mullards. Nothing swirls like certain NOS, or lasts 12,000 hours either.

What do you think about the new Tung Sol?

 

[Russ]

I just don't understand why they can't make them like they used to. It is proven that they can because they did for years. I think that it is just that they choose not to. Realistically we could be playing new production that would certainly rival if not bury the old tubes. I think we should all protest and not buy current production until they offer a quality tube. I think that if globally we all said hey your tubes stink that the manufacturers would get the hint. I also think that there should be a minimum life expectancy that exceeds 10,000 hours. In addition to this, I feel that manufacturers should take the time to select through the tubes and just throw away the tubes that are not up to snuff. Unfortunately, there is too high of a demand for tubes for this to be realistic. Also, businesses would just sit on the old stock until they could off load it anyway. I guess we will just sit in a world of mediocrity and be left saying, "I wish they still built them like they used to...."

Like anything else I guess tubes fall into the category of disposable and also like anything else we generally expect them to fail eventually. It is just too bad that as consumables they can't be a little nicer. I think that there are enough tube connoisseurs though that we could make a point to the manufacturers by not buying tubes. Although those that use them professionally would not care to partake in such a scheme. I was just noticing that many touring bands are changing out their tubes every couple weeks whether they need to or not. This is a waste though a nice preventive maintenace measure. Must be nice... I think it would be nicer if they were still making quality tubes though.

Sorry for ranting but it makes me sick to no avail that with the current technology to see something as simple as a tube not being manufactured as well as possible. They can do just about anything with today's manufacturing technology but it seems that they can't even match yesteryear's consistency and quality...

 

[Boogiebabies]

I really see your point but, back then they had medical devices that ran on 50 Mullard 12AX7's and someones life depended on it. Also, the US Military had tube transmitters in everything from F-86's to Bombers running tubes that had to perform and perform to military specs for shock, G-force and longevity. Today, the tube manufacturers would not be able to survive if they had a customer come back only every ten years for a re-tube. The other day I was talking to an acquiantance. He was complaining that his 67 Twin was retubed and he hated it. It had lost all the magic it once had. I said, well you bought it new in 67 and never retubed it. It had original RCA Black Plates and the original preamp tubes.
His tech put JJ's in an he is yearning to get his tone back. I said, " dont be afraid to drop a few hundred on some NOS RCA's" and all I was a gulp! They just do not make them like they used to due to the economy of scale we have now. I think that GT is trying to pull valves back into the glory gays of production with their in house USA production. We should all be happy that Mesa's dont run on 300B's. OUCH !!!!

 

[Russ]

no kidding.......

I am thinking more and more GT is the way to go. Granted you pay a little more but they are screened better and you can still get most of the major varieties. You can even get high gain kits and MPIs. I am glad to see that they are taking matters into their own hands. If I had a few million I would retool an old tube factory and being production just to try to increase quality. I know that at least audiophiles and musicians would be into them.

Those old black plates were something special. There is no doubt that he would be bummed out.

So you like the C9 Boogiebabies?

I have one of GT's and it sounds ok but I guess compared to other current offerings they are worth the price.

Have you tried the GT JJ?