Thanks guys. I thought that's what they were, but was concerned about them melting. The two I have don't have the sp designation, that's why I was wondering. I thought I had read something about the sp's having the dampers, but had never seen any. Again - thanks.
They are the more expensive Meas 12AX7's. You can use them in different positions (V1 - V5) to alter the tone. Not as much as using different manufacturers, but there can be a slight difference. I think I use them in V1 and V2.