This is my all-time favorite headphone amp (sans DAC). Runs 100 hours on a charge, and the rechargeable batteries are common AA NiMH cells. And it sounds very good.
http://www.hifiheadphones.co.uk/for...ric-avenues-pa2v2-2-headphone-amp-review.html
http://www.hifiheadphones.co.uk/for...ric-avenues-pa2v2-2-headphone-amp-review.html