Tubes Asylum: Careful consideration is still neceassry by Bambi B

Len_,

It's interesting you have different data for the 7308/E188CC. I thought this was all standardised- we could assume a tube might be capable of handling more current than the rating but not less. I'm going to check this,...

You're correct that in a lot of cases the tubes of the 6DJ8 family can interchange, but I can verify there re important reasons for the 69322 and 7308 in terms of being less microphonic, longer life, -and importantly be able to be pushed harder. I actually had a little Audio Research "club" of 6 correspondents with SP10 preamps and we all spent most of out time discussing tubes that wil survive. Remarkably, every SP10 owner in the club either has or had also used an ARC SP8 and spoke fondly of the easy life of the 12AX7 ! One fellow even made on commission more or less a new SP10 using 12- NOS Mullard M8137s- a really super 12AX7, instead of the 6DJ8s ! Another SP10 user cheerfully changes Amperex Bugle Boys in his SP10 every 100 hours- he has a huge pile and thinks the sound is worth the sacrifice.

Personally, with Dutch frugality, when I wasted just two Amperex A-frame 6DJ8s in about 50 hours and a pair of rugged Siemens 6922s- two of the most expensive tubes I've ever bought- in about 200 hours- they just became noise makers- and that was it- and I know I'm spending the rest of my life with 7308s and Russian 6H23n-EBs. So will other SP10 and Audible Illusions Mod3 owners I expect.

I would reassert that care is needed in considering whether a 6DJ8, 6922,or 7308 is the right tube for the job.

Cheers,

Bambi B