Wow, perfect! This solved my problem! Works on Galaxy S3 Neo as well, and also creates mono bluetooth output! I've built a bluetooth mobile speaker box with a built-in amplifier and battery. I'm only using one channel of the stereo amp. I was already looking at some other solutions for mixing stereo into mono using passive resistors before the amp, but it's much easier to solve the problem at an even earlier phase, from software! :) (The bluetooth amp doesn't have aux input and I can't get to the signal before the amp, it's all integrated on a board...)