Right channel distortion/crackling when connected to compute

Question

Hi,
When I connect my ipod to the computer (even if its unmounted) the right channel of the audio out crackles and stuff, why?
This occurs on my iBook, and Dual MDD G4
Grounding loop?...If so, quite disappointed, could someone please confirm.
Method:
Connect iPod nano to computer using the USB cable.
Plug in headphones
(the above can be done in any order)
Place headphones in ear.
Songs don't have to be playing, just headphones need to be plugged in.
I have tried with grounded speakers and have no problem.

Answer 1

As you probably know that the tailpiece is grounded along with the pickups and tone and volume pots.  We know that it works because when you touch the tail piece the crackle stops.
I had this crackle once when in a hurry I used a speaker cable. But seeing you tried two cables with the same result we need to look elsewhere. The only thing I can think of is interferences from a light, electric motor or cell phone or a bad ground.
Make sure your mac is plugged into a properly grounded wall outlet.  If you use a power strip plug into a wall outlet and see if it goes away. Also turn off lights and cell phone. Move your interface away from your mac and powerfully speakers.