This article discusses the PX22, but the same steps apply for the Z22, Shadow, Spectre, Marvel and Atlas headsets.
To use your PX22 on a PC, you must connect BOTH the in-line amplifier's black 3.5 mm plug and its USB plug to your PC, then properly set your Playback and Recording devices in Windows.
1) Make sure the headset's 3.5 mm plug is connected securely to the jack on the in-line amplifier.
2) Connect the in-line amplifier's black 3.5 mm plug to your PC's green Line Out jack (or headphones jack).
3) Connect the in-line amplifier's USB plug to an open USB port on your PC.
4) In Windows 7, go to Start > Control Panel > Hardware & Sound > Sound > Playback tab.
(In older versions of Windows: Start > Control Panel > Sounds > "Playback" tab.)
Right-click "Stereo Speakers" (or something similar) and choose "Set as Default Device". NOTE: Make sure your default Playback device is NOT set to "Turtle Beach PX22". If your default Playback device is set to "Turtle Beach PX22", then the Chat dial will control everything and the Game, Bass, and Treble dials will control nothing.
5) Next, click the Recording tab. Right-click Turtle Beach PX22 and select "Set as Default Device". Right-click Turtle Beach PX22 again and select "Set as Default Communication Device".
6) If you use a chat program such as Skype, Ventrilo, TeamSpeak, etc., in your chat program, set Turtle Beach PX22 as both the input and output device there.