HUMM! imac>1/8line>1/8 to RCA plug>sony ss2000

im experiencing a loud annoying HUM in my system.

my connections goes as follows.


IMAC ( with and without griffin usb iMic)
1/8th headphone jack extender
1/8th to rca converter ( red and white )
Sony SS2000 HTIB


the only combo i've found that works is connecting the imac directly to the box with a long RCA(red/white ) line.

Problem is, i already ran the 1/8th through the walls to the HTIB.
( i've confirmed there is no interference with it, as it does the same thing running a seperate headphone extender to the box)

any ideas what could be the problem here? i hope the headphone extender is not the problem? what are my solutions?

it's an 2.16 ghz intel core duo 2 ( the white one )

like i said, i was able to get it to properly work connecting rca plugs directly from back of ss200(HTIB) to the imac via a converter.

is there any sort of device i can put on the ends of the 1/8th line to prevent the hum? why would it be humming in the 1st place.

problem solved with the Ground-Loop Isolator from radioshack.... jeez, that thing is amazing.

(Cost)
the reason why i opted for the 1/8th line is cause i was running it 50 feet or so.



other then that, i doubt i need anything more- it's just for viewing itunes movies on my TV