Right, since my Blackstar takes 3x ECC83's and 1x ECC82, what would happen if I switched it out for another ECC83? I ask because I have a spare ECC83 lying around, and I think the ECC82 has actually died on me.
Proably nothing bad - they just differ in terms of output, right?
Just googled - yeah, the ECC82 is a substitute for a 12AU7, in American parlance. IIRC, it has 50-70% of the gain of a 12AX7/ECC83. You almost certainly won't hurt anything by trying it, though depending on what the tube is doing you could get interesting results.
Does Blackstar provide you with the same sort of detailed specs as Mesa? Any idea what the ECC82 is actually doing in the amp?