My new laptop has only one 1/8" port for connecting a headset with a mic. I am trying to find a way to perform the sound card calibration but I haven't found a way to make a loopback cable. I have tried making my own by taking an old 1/8" plug and shorting one of the output wires to the mic input wire which then causes my soundcard to disable the mic input. Has anybody else found a way to do the sound card calibration when your computer only have the one port?