They all use the eight-pin octal base. I’ve never seen an 6SN7 with the ST glass envelope. Chinese company Linlai makes some with the odd shape envelope.
Help with Cary SLP-98
I'm interested in using 6SN7's that have a larger base and or different shape than the conventional 6SN7 tube. Can anyone help with a recommendation for a socket extender that fits, or other options?