A7N8X-E Deluxe Sound problem - 'bus noise'

Have just noticed that my new ASUS A7N8X-E Deluxe m/board (with
built-in nVideo nForce sound circuitry) puts out a bit of 'bus noise'.
I've only just noticed it today when using headphones for the first
time on this setup.

The Line Out of the sound circuit is connected to the Aux input on my
Hi-Fi's amp.

I *used* to have this problem on my old AWE32 ISA-based sound card (on
an ABit BH6 m/board), but muting the Line In fixed that. However,
muting/adjusting the volume settings for the various I/O on this new
board makes no difference to the 'bus noise'.

I'm sure it's not my Hi-Fi at fault, or cabling, or headphones etc
because, as noted, I eliminated the problem on my previous setup.

Any thoughts please anyone on a solution?



Ta,
Phil