Ap1 and ap2 are supposed to sound similar.
Ap1 upgraded for pure power can't work without the battery pure power.
Buy pp before a ifi USB or better USB cable.
Buy a better USB cable before ifi USB.
With all that, software still have a big impact on the sound.
So the filtration, buffer, reclock and isolation are not perfect and the better the source, the better the output.
Enjoy the world of audio.