That was the subject of a new thread yesterday. Apparently no one had tried them yet.
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I have used many different iterations of Telefunken 6DJ8 variants, and older is a lot better. In order:
1. 1961 Telefunken 6922 specially selected for HP
2. 1964 Telefunken 6DJ8 specially selected for HP
3. US Amperex wasp wasted 6922
4. Early Dutch Amperex 6922
5. 1962 garden variety Telefunken 6922
I was just entering university back in the day, and could never understand why HP tubes were SO SO SO expensive. Then I moved to California and heard the stories about HP taking over their own tube testing, and DUMPSTERING 95% of the premium 6922's they tested before certifying them for their test equipment. Well, they did instrument the moon shots, after all.
Then I found a few of the early Telefunken 6922's with Telefunken seals under HP seals. Nirvana. In my ARC SP-10, if these were a 10, the US Amperex waspwastes were a 7. Really. The early T/ HP were that good.