Sound Issue

[Shanez]

Hi folks, right so my problem is this.

Im trying to record a mix from my decks to my mac using an rca/jack cable. This is the way ive been doing it for months with no problems, but recently after i record a mix and play it back there is feedback (buzzing humming noise) but i only hear it when i play it back and not while recording so its not my speakers (hi fi)

I moved the speakers away from my mac incase that was an issue, changed nothing.
I bought a new rca cable, still no change

I am using adadeus pro to record, so i tried audacity and still getting the same issue.

I then got my sis's laptop and recorded a sample to that and it worked, no feedback! So it has to be a problem with the mac but i dont know what to do? Any ideas?


Intel High Definition Audio:

Audio ID: 12
Available Devices:
Line Out:
Connection: 1/8 inch Jack
Headphone:
Connection: 1/8 inch Jack
Line In:
Connection: 1/8 inch Jack
Speaker:
Connection: Internal
S/P-DIF Out:
Connection: Optical
S/P-DIF In:
Connection: Optical

[Shanez]

It could be the power supply unit maybe and/or the capacitors on the motherboard a friend told me this, is this bad?