Locate the PC volume control. A single click on the volume control icon will indicate the current default playing device. If not already set, you can choose the default playing device from the drop-down menu: Choose Speakers (USB Multi-Channel audio device). The device might also be identified as 2 - USB Sound Device. However, make sure you don't choose Digital Output (USB Multi-Channel audio device).
An alternative way to set the default playing device:
The volume control menu is slightly different among different versions of Windows. Therefore, you might find this alternative way useful for you:
1. Right-click the volume control icon ==> Sounds (or Playback Devices) ==> Playback tab (You can also open the Sounds dialog through the control panel).
2. Right-click USB Multi-Channel audio device and ==> Set as Default Device.