I have this amazing sound card
http://www.lynxstudio.com/product_detail.asp?i=12#
And with the sound card at max 63, I don't get any clipping.

I am still not sure if I will use the digital clock of the SPDIF, or use the internal sound card clock who seems to sound a little bit better.

To get sound, I had to remove the 'Digital In Mute on error' option of my sound card !