mp3 player powered from usb but using headphones

I want to connect an mp3 player to mini speakers but power from a powered usb hub. When I connect the player to the hub, it prevents the mp3 player from being used as a player. Anyone know a way to do this? I want this for an 88 year old blind person to have music access. She does not have the ability to tune a radio and she has poor radio reception in her area. This way I can change out the mp3 with different songs periodically. Thanks.