Maybe some people are more immune to electrical shock than others. It is not the voltage but the current that kills. I worked as an electrician on systems from millivolt WWII ear signaling to MV which is 15KV to 45KV. I never took any direct shocks on any system over 600VAC nominal, but got nailed by 120, 240, and 277 a few times. I still think finding the B+ of an old Valco Supro which was located in the most dangerous place inside the amp anyone could ever find was one of the worst shocks I ever got. I did get nailed by a 7500 volt hi pot one damp rainy day. That was pretty painful too. Maybe I am lucky. Working with electricity 40-84 hours a week you will get zapped. I have seen some people with holes blown in them from 120 volts, and worse from 277. I have no clue why it just scares me and makes me jump, and other people have died. AS one person said, "Keep one hand in your pocket" as it is great advice so as not to pass current across your heart. Also make some jumpers with a 1K-10K resistor to put across filter caps. They can actually recharge themselves and nail you after you think you have shorted them and have them discharged. Some say they draw energy from other caps in the amp. I have been nailed by them after reforming the things and discharging them upon removal from the power supply and load. They can be fine right after taking them off my reforming rig then you pick one up an hour later and get a surprise. I have been using some old Koss ESP10s, and Staxx electrostatic headphones. My only complaint is the 1970s Marantz amps won't work with the Koss due to a negative feedback loop, so I have to use another power amp, and I do not want to drag one of the tube amps into the shop area.