how long do these last?

[Chuck H]

I don't think you will be so confident stating that I am spouting "hogwash" after the tests.

Sorry for that. Uncalled for and I apologize.

I do agree with your scientific test method (with one exception that I will qualify later). And I think it could clear a lot of air. I know that your in the camp that many currently made tubes barely qualify their designations. I've read that in your posts. I think this too. It would be nice to have accurate data sheets on these tubes that are similar, but different. Without such information though, your test would prove too exhaustive. Every tube would need to be evaluated first so that it's operating parameters could be equalized. Perhaps you have equipment to do this. In fact I'd bet that you do because you've posted about doing this very thing. And I hope you will. I'm stuck plugging these slightly different tubes into the same circuit for purposes of evaluation. So, even though I was crabby about it, the reality is that it's not fair to the tubes. Now...

The material should be moderate level, within the most linear portion of the curves for that tube in order to hear tube differences. Driving harder and you hear differences in the onset of non-linearity that has more to do with the circuit and gain of a tube than any sound character added to the signal simply by being amplified by the tube stage.

WRT guitar amps there are many circuits that distinctly contradict this criteria. And that's significant. I can only say what I "believe" because I have no test studies to present. And that's unfortunate because your fairly stringent about knowing rather than believing. Fine. But to reproduce circuit induced non linearities may well require still more exhaustive tube data research. Even then I just don't "believe" that, for example, a Sovtek 12ax7WA would sound like a Sovtek 12ax7LPS. Though I agree they are different tubes, even if these differences are accounted for I still think they would sound different. Especially in a non linear environment such as might be found in a guitar amp. Though I can't prove that, I don't think I have to for anyone familiar with these two particular tubes. And it's glaring examples like this that are the basis of my very unscientific beliefs.

Peace