Yep, I'd have to see waveforms. My instinct is that the phase is causing some distortion somewhere along the audio path, between the signal (the ideal) and the

Yep, I'd have to see waveforms. My instinct is that the phase is causing some distortion somewhere along the audio path, between the signal (the ideal) and the analog. Between that is the DAC, the amplifier, the wiring, and the transducers, all of which can induce distortion of varying degrees based on various properties of the input. But your experiment validates the simple concept that small, seemingly insignificant differences in audio can cause unexpected and perceptible effects! Awesome.