A few months back, I built a battery box specifically to use with my AT853C-ELE caps. It is more or less a "3-wire battery box", like the one that is pictured with a schematic in this forum. The box worked great with the mics. I recently ordered some AT U853 hyper caps (new series), and figured I could use the same battery box with them. Apparently, I was wrong in my estimation. I don't understand why, but after 20 seconds of testing the new hyper caps with my box, the sound died, and the 9 volt battery was actually hot to the touch and completely drained. This was an almost new battery. I don't see how the caps could use up so much energy in such a short period of time? Has anyone else had similar results with the same gear, or think of one reason why this happened?