I just bought a pair of M50's with Aluminum capsules. They hadn't been used for some time. I wanted to make sure everything checked out so I hooked the mics up directly to a trusted power source and brought the voltage up to 701 volts as per the note on the schematic, I think its called a schematic. The mic started smoking and sputtering and smelled pretty bad and it doesn't work at all. I'm thinking it might be defective. Probably going to hold off on the other mic for a bit.