Originally Posted by tk3
I changed the stock EH12AX7 for some New Sensor new production Mullard 12AX7, and couldn't hear much of a difference.
At least, I doubt I'd be able to tell the difference in a blind test.
The Mullard (relabel) and the Electo Harmonics 12ax7 are pretty much the same tube. It's the same with the EH and the Tung-Sol relabel ef86/ef806s. Both are distributed by New Sensor, made in the same factory, same internal design.
Probably 1/4 of the tube amp manufacturers official stand is that different tubes make no difference in sound. Some reviewers used to say the same thing but most of them agree that there is a difference. For designers, there's lots of reasons that they might say this but I believe the main reason is repairs and the warranty issues that bad tubes lead to. Another is that the designers made decisions on the tube "type" used in a particular position. The differences in sound is
very subtle compared to the sound of a 6sl7 compared to a 12ax7. And when a design goes into production, they are off to the next design. It may be an upgrade of a current amp with maybe some different power supply regulation and the differences here would not be subtle either. So, when a designer says that changing tubes don't make a difference, ask them " compared to what?" and they might say, "well, more than changing cables of course,.." ( which I've heard a couple of times). Just remember that during the design process, there may have been 10 prototypes or there may have been 100 variations of 1 prototype. Either way,each one of these changes resulted in huge sonic swings. After all that, it's no wonder that some of them say that tube rolling doesn't result in a significant change in the sound.
The last major reason is cost. Or rather, relative cost. What I mean by that is designers are constantly trying to build gear to meet a price point. The better designers do their best to give you more goodness per buck than their competitors. But, to meet that price point, they have to cut back on that teflon cap or bigger/better iron. So when you start talking about spending $120 on a pair of NOS tubes all they can see is that MagnaQuest transformer that they had to downgrade ( lowering the parts cost $100) to meet the price point. So, in that case, the difference in sound is insignificant compared to the improvement that the big iron would have made.
So, you might ask why they can't hear some improvement and admit that it helps the sound. I mean, don't these guys tube roll too? Not if you don't have an amp to do that with. Lot's of small builders can't afford to keep any of their production models and the ones that do, are sending them all over the world for demos and the only time they see it is when it gets broken.
Just remember, tube rolling voids warranties. If the designer recommends it, than he has to honor the warranty ,..right?