kartoffel said:
Just tried these on my MKIV and it sounded great for about 2 minutes. then all the sudden it sounded like when the tv goes out and you see black and white things going all around. Static galore so I put the old tube back in wonderful again. Not even 2 more minutes later the clean channel sounds like a sin wave bell tone. I tap the other =c= 12ax7 and well I guess that's what they call microphonic since none of the other tubes do that while taped. **** they where expensive too
Edit: It did however sound noticeably really good before the problems. I wish they where not so expensive because if they worked they would be so worth it.
One of the problems with new production tubes is the lack of consistency in production quality. You just found out. Bummer. That is exactly why Mesa Engineering has a "robotube" testing unit and why they throw away so many tubes that don't meet their standards. With that said, and that is a compliment to Mesa, I collect vintage tubes because I like their tones better than new made stuff. And I do get some lemons. Goes with the territory. If you think that your Svetlana 12ax7's are expensive, then price some Mullard 10m 12ax7's on eBay. :shock: Peace.