Hi Richard, A dac can give you better sound from mp3 files. Really, what might be happening is that the phones are driven better by the amplifier in the unit, as opposed to the crappy one that is part of most portable digital devices, but the end result is improved sound. I use to have a low end portable amp plus dac that was kind of a pain to operate, and you could definitely hear the difference with my akg q701 phones.
Mary
