The audio cable consists of a length (to suit your needs) of shielded audio cable and a 1/8" (3.5mm) stereo mini-plug (Jameco 231175CB). Connect the center conductor to the center/tip of the plug. The shield is connected to the case/side of the plug. Leave the center ring on the plug unconnected. Although your headphone outputs are stereo only one channel (L) is used to capture the audio stream. The center lead of the audio cable is connected to the Audio In terminal and the other to GND.