Re: shutting the power supply of guitar pedals
I just looked up a couple of things to solidify my POV on this and learned a couple things.
First, tubes aren't incredibly picky about powering down in general. It's powering up they don't like to be rushed on. Voltage variances when an amp goes from off to on and, say, a guitar player is fiddling around on his guitar while the tubes are heating up..that's when tubes can get beat up a little.
Second, your tube distortion is going to have a solid little 12a-7 in it and instead of running at 100-150v plate voltage, it's almost guaranteed to be running "plate starved". You're running normal pedal voltage of 9-18v in it and the tube is acting as a clipper like a diode.
It's the equivalent of running a hose with a trickle of water. You're not going to do much to it.
I'd say, in my unprofessional opinion, that you're still fine just pulling the plug. If you're worried, maybe run the pedal into a surge protector and then the wall?