Free High Quality (Benchmark/Test/Reference) Audio Files

Hi all,

I need to test the audio output quality of my sound card , phone , tv and also my headphones.

Does anybody know a site where i can download specially prepared for Auido test purposes? I am aware that there are many reference audio cd's especially for output quality of car audio systems but i do not want to pay for them or download illegal copies. I need a freeware site which provides this kind of recordings.

Thanks