From what I can tell, the Big Brother is using a boost circuit, not a step-down. It says it is using the 2x14500 batteries in parallel, meaning it's at 3.7V (4.2V fully charged), but he's doubling the amps by putting them in parallel. So yeah, his circuit has to be raising/lowering the voltage using the pot. It's working just like the Provari but without a display.