THX has been applying its grey cells to the power amplifier, as THX grey eminence Laurie Fincham explained. The prototype shown uses what he calls a Class ABC topology with newly tweaked rail-switching power supply and compact ceramic (as opposed to bulky electrolytic) capacitors, all run off a lithium iron phosphate battery (yes, iron, not ion). In the picture you see a super-skinny two-channel output stage; adding capacitors would make it only 25 percent larger. Anyway, the result is a powerful low-profile amp that runs cool and efficient, avoiding both the power piggery of Class A and the problematic performance of Class D. And yes, it sounded great with Sonus Faber speakers and Steely Dan's "Gaslighting Abbie," achieving both well controlled bass and a high degree of overall transparency. Why this, why now? Fincham points out that his team is liberated from the tyranny of the product development cycle, enabling them to take a longer view and to incorporate ideas from the entire history of audio going back to the 1920s but also including the latest tricks. For example, the type of battery used is relatively new to audio but has been deployed in things like power tools and electric bikes. The THX amp design has yet to be built into licensed product but current licensees are getting their first look at this show. Potential uses include everything from inexpensive compact products to BD-receivers to high-end multichannel amps.