In reply to your question re. the power supply, yes, that's how mine looks too.
Regarding the hum, mine makes all sorts of hums and noises, but so far I've always blamed the fact that it's connected to a PC, and it really makes no difference how far from the PC I move the BB, since the AUX cable still connects the two devices.
The variety of hums and whirrs seems to depend on a lot of factors: the PC screen, my radio mouse, the PJB headphones, all of their wires functioning as antennas, and the bass guitar and its lead adding their own earthing/screening problems.
I can't remember whether it was less noisy when I first got it (it's on permanent loan from hubby). Curious to hear if others have the same.