My late father built a 4-1000A linear, grid driven, that was by far the most rugged one I ever used. It would do full legal power without breaking a sweat. It's still sitting in a garage in California, and every time I go there with my pickup truck, my brother tries to get me to take it home. Unfortunately, I'm afraid the power transformer for it might exceed the GVWR of my Tundra, and I don't have a forklift to handle it - it's an old 'pole pig' with a huge iron core that is marked '1919'. It looks like something out of Frankenstein's laboratory. I saw a design for a solid state switching power supply that ought to provide the HV for such a device, and probably weighs 1/100th as much as Dad's old supply. Someone I knew built a 4-1000A amp as his senior project in the EE program at San Jose State. When we fired it up for the first time, it started to self-oscillate at very close to 27 MHz.. The wiring error was soon corrected.