I would recommend the Siemen CCA's in your VK 30. They are among the best in the 6 volt 9 pin family. I have not had a good experience using the 6dj8's in the BAT preamps. Other peoples experience may vary.
Tube handling/designations
I recently purchased a BAT VK-30.It came with 6922 Teslas installed as well as the original Sovteks.I would like to try some different tubes to see how they affect the sound.My first question is do you need to wear gloves so as not to get oil off your hands on the tubes like halide lights?My next question is are 6922's the only tube that will work or are there others?I ask this because in some ads for tubes I see a slash followed by EE????.Also,what does NOS mean and why are they supposed to be better?