preout clipping on headunit

I want to know how do i determine clipping on radio preouts with an o scope. i have a test cd with  1khz,50hz,and pink noise which one of these should i use while testing i want to know the highest volume i can use without clipping.

If you have an oscilloscope, you really need to play several discs that you would normally be listening to. Clipping is called clipping because it appears as though someone has clipped the top and bottom half of the waveforms off. The following page has a picture of a slightly clipped audio signal, about midway of the page. 2 pictures below that one is a good picture of a severely clipped sine wave. http://www.bcae1.com/settinggainswithscope.htm