I don't know why but there is the difference. You can ignore the topic of power management, or you can discover a lot of new things by trying a high-quality power distributor, power cables. There is also diference in interconnects, usb, used player (I like foobar2000).
Some tips. It is better to use connectors from the same material as in the power outlet and the power inlet of the device. Gold-plated materials usually slightly softens and darkens high frequencies. 2 meters is more difference then 1 meter. Without shielding, the sound is usually freer and more dynamic. The ground wire may not be used; in some cases, this may worsen the result.