Brent tells me he sees this problem with modern tubes not fitting old sockets well, especially in the Chinese tubes. He recommended some socket savers from Antique Electronic Supply. I ordered a few and will leave them installed in the tester.

Will, I bought my third quad on fleabay. Here is a current auction for two. Hope that helps.

Greg

Will I did see that, and it was one of the reasons I felt the "investment" was worth it with Grant Fidelity. The only way to know for sure will be to swap out whole quads in the Torii.

Ehh...  one can get a matched quad of the 6ca7s for about 50% of what Grant Fidelity charges from a source that has never steered me wrong.  On the other hand, I the one premium pair of Shuguangs I got from Grant (Psvane 845) left me feeling numb and was ultimately sold.

My personal feeling is that its effective marketing.

My third quad was picked up from this auction. I am not complaining, but the fact that it was one of these tubes that broke an octal post when testing, and that my seller has disclaimed any interest in assessing the cause, causes me to ascribe ome value to the Grant Fidelity overhead price. So, best I can do is compare the two, continue testing (once I get my socket savers in), and see what happens.

I do think Grant Fidlity makes some valid points about how matching alone does not provide the necessarily most predictive results. OTOH, it may well be that the 100% markup cannot be justified by any amount of longevity. Don't know. Yet.

Thanks Gopher. Are those guys affiliated with the same people who make DACs, headphone amps like the GD-Audio Phoenix, and other stuff?

Anyway, looks encouraging. I put in an inquiry on the ST 6CA7-Z.

Thanks Gopher.