Are most power tube bases the same dimensions?

[Tonegeek]

I am building a amp that can use EL-34, 6l6, 6550, etc. My amp will be a tubes up design and I will probably get sockets from allenamps if the bases are all the same. They use a Fender style clamp so if the bases are not the same then I will look for something else using the spring holders.
thanks

[jaysg]

The Fender hang down clamps won't work...plus I just broke a couple (not really Fender). The 6550 & KT88 have larger bases than the 6L6 & EL34. I actually have an EI set of EL-34's with a smaller base than usual, fwiw...more like a 6V6.

I would buy a set of hat clip & springs for large bottles -- 6550 and use those for the rest of the tubes. You might have to connect 6L6's lower on the springs.

[CaseyJones]

Octal bases in general go small, medium and large in outside diameter. The smalls would be EL34 5Y3 5AR4 6F6 6K6 6SN7 6SL7 6V6 in general. I think U.S. 5881s and 7591s use the smaller base.

6L6s and 5U4Gs use a larger base.

6550s especially the metal banded types use the largest base, they won't fit into a Fender style clamp at all.

Make a go / no go guage using a Forstner bit and sort through a pile of octals if you're in doubt. I don't have my tubes and verniers within easy reach at the moment or I'd give you some exact dimensions.

[Structo]

I know when I switched from TAD 6L6's to JJ 6L6's the JJ's had a smaller diameter base.
Then I switched to Winged C's and they seemed somewhere in the middle.

[Firestorm]

There's a little bit of a range in octal sockets. The smallest one is just 7/8"; then 1-inch; next there's 1 1/16"; then 1 1/8"; then 1 3/16" (Beltons). A little variance in mounting too, although most mount on 1 1/2" centers. And of course, some are top mount, some are bottom mount and some go either way.

If this is a tubes up design, you can get away without any clamp unless you want to stabilize the amp for transport. You can't use the Fender type with 6550s or any kind of KT. The clamp won't grap the metal base (and if you did the fender thing and used Pin 1 as a mounting point, be forewarned that some of these tubes have the metal base connected to Pin 1). For maximum flexibility, go with the spring clamps, but even these come in two sizes: EL34, 6L6, 5Y3, 5AR4, maybe 5881, and then bigger ones for 5U4, 6550 and the KTs. One other thing to think about when using the 6550s or KTs -- these guys like to have some ventilation so you'll want to mount your sockets farther apart to accommodate them.

[Tonegeek]

Thanks much for the informed replies. I will be giving my sockets some room to breath and using no clamps.