The X3 has a stereo analog input, which will accept any stereo line level from
a portable CD or MP3 player, PC soundcard line out, DVD player headphone out,
stereo receiver headphone out (requires a 1/4" to 1/8" adapter), and so on. 
For TV connection it requires a 1/8" to 1/8" Cable. These cables are easy to 
find, available at your local Radio Shack. 

The X3 headset *microphone* however, will not work with a PC soundcard 
because it is designed specifically for the Xbox 360 and Xbox Live Chat. 

If you want to use the X3 with an audio player that has a Digital Out, 
please have a look at this article:

Ear Force X3 - Connections - How to Use with Xbox 360 Optical Digital Output:
http://support.turtlebeach.com/site/kb_ftp/609319962.asp
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