TIP50 for HT regulator

At a local ham fest I picked up 100 of 150V zeners so I thought I would build myself a stabilised 300V HT supply - not big current, just enough for my mic pre projects. So, I have been looking at high voltage transistors and came across the TIP50 which are rated 400/500V. I picked this oas it the only one whose number I vaguely recognise.

Has anyone used these for HT supplies or what else do you use?

Cheers

Ian
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