I recently got an Astro mixamp with the A30 headset. In order to use its mixing capabilities, it requires two sources of audio input. One being USB (also used for power), and the other being either optical or a 3.5mm speaker connection. My sound card doesn't have optical so I have to use USB and 3.5mm speaker output. However windows only allows me to output through one mode at a time, meaning I can't use the mixamp properly. Is there a way to output through multiple sources? Or another fix that I haven't considered? Thanks!