Mick & tube rolling: I totally understand his position... he is a manufacturer and it would be illogical to build a product which is optimized for rare tubes - plus, he cannot spend all his time answering email questions about what tube works & which do not, what tubes sound the best and which do not.
Admonishing tube rolling is the only logical answer.
Every system is different and so is every tube - this is perhaps one reason why everyone has their favorite tube combo.
Regardless of how Mick "tunes" a Supratek to sound, there will always be something (tube combination) which sounds better for each system. Unfortunately, there is a lot of cancellation & reinforcement which goes on in building an audio system - to create balance - a simple example would be a bright system being made better with warmer tubes. This is a necessary part of audio & regardless of what Mick says, or how he tunes a Supratek (and for which tubes) there will always be compensation required (or equalization) in order to truly optimize a system. Mick can only tune a preamp based on HIS system and room. Plain and simple, HIS listening environment is different than anyone else's.
Yes.. different tubes can change the operating parameters of the Supratek. In my experience, changing those parameters were a necessary part of getting the most out of the Supratek. If Mick spent time "tuning" my preamps, then obviously he didn't spend enough time on important tuning details like asking me how I liked my music to sound.. or asking about my other components, etc. As good as Mick is, his tuning can never be as good as mine - sorry Mick.
Since it is impossible for him to know all of us, and listen to all our systems, Mick must make assumptions in his tuning. Those assumptions will most likely not work for the vast majority of us.
One of the greatest strengths of the Supratek is the fact that it can be tweaked so easily with tube rolling.
