TX-SR309 & iMac noise problem ?

Just got my TX-SR309 amp & very happy with it.
1 problem -
When I run my iMac 27in into the amp I get a lot of noise interference ?
I've tried many things to test and no joy. For example -

different inputs in amp ( aux / BD/DVD )
imac headphone out / Saffire sound card
turn off wifi / bluetooth, etc on iMac

Don't have the problem with my iphone / macbook pro.
Output from iMac noiseless when not running through TX-SR309.

So I'm pretty certain that the problem is between the iMac and the TX-SR309 amp.

Don't want to return the amp but may have to ?

Can't seem to solve it ?

Help !

Hi flippyfloop,

Macs are not supported. You may on the other hand aquire a 3rd party software that is windows based that can help with your issue.