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A DIY electrostatic amp for intermediate DIYers? - Page 40
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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.
Has anyone started making any plans for the electrostatic headphones? I have some transformers that are too high a voltage but too low current to do much else with. I have a beefy one that with a doubler comes out to 700VDC plus, but I have been using those in pairs and making the current high enough to drive some nice tubes along at 77 watts. I used something like KT88s only with a plate cap. They take 800 VDC easily. I ran them through a pair of Partridge designed transformers I had wound with 1,2,4,8,16 ohm taps and 100 volt out for a PA distribution line. Sorry to be cryptic about the tubes I use. For now these are affordable in the Mullard or GEC UK made brand. (affordable on my monthly pittance anyway) My doctor bought the AR RT600s and $10K in 6550 tubes. I would love to know where they went. The govt seized all his stuff for fraud, and some other DEA violations. 600+ wattsx2 in a house? Oh well to each his own.