I've a DAC for headphones (GeekOut 720) which has two output jacks with different impedances: 47 Ohm (with a large headphone icon next to it) and 0.47 Ohm (with a small headphone icon next to it).
I'm currently using Sony MDREX110AP headphones, with 16 ohm impedance according to its specs. When I connect them to the 0.47 Ohm output I get much louder output than with the 47 Ohm jack, which makes me wonder, shouldn't the smaller impedance output drive my headphones with less power than the larger one? If such is the case, why is the response louder for the larger impedance output? It seems to me that I'm not quite grasping the output impedance concept.
Bonus question: what output should I use to get better sound quality and protect my headphones?