This is my 4" x 24" new & improved junk box coil powered by two series MOTs with no voltage doublers, no RF filter, and no ballast. Supply voltage is only about 4800VAC, but with insane current. The only change I made to the coil was to close the spark gap to a point where it could just barely fire. Streamers were only about 36 inches (1 meter), with an occasional 48 inch (1.3meter) hit to the ceiling and a rare strike rail hit now and then. The sparks are very thick and intense, no doubt owing to the ludicrous pulse-per-second rate, as the tank cap is only .047uF. I'd love to try this with a 0.1 or 0.2uF tank cap to get the bang size up and the pulse rate down.
This was a very simple, low-budget experiment to test the feasibility of using nothing but a pair of unmodified, unballasted MOTs to fire a Tesla coil at low voltage and high current. I hope to try it again someday on a coil optimized for such a power supply.
A couple of interesting points. The spark gap overheated quickly, limiting my runs to no more than 20-30 seconds due to the formation of a power arc. This power supply needs a better quenching gap. A couple of tungsten or stainless steel rods blown with 90psi shop air comes to mind. Also, while shooting the video from which these frames were captured, the camera experienced an auto shutdown. This has never happened before, and I was afraid the fierce RF energy had killed my little JVC camera. I recycled the camera power switch, and it was fine. Spooked me though. I'd sure be ticked off if my cheap coil killed my expensive cam corder.