The VDA_USB (unlike the VDA_PCI) includes an Audio Capture chip to allow 
for an entry port for the sound to be captured. The VDA_PCI uses the system's
Sound Card for both Audio Capture and Playback, whereas the VDA_USB uses the
included AC97 Sound chip for Capture only and the System's Sound Card for 
Playback. 
 

Here are the Specifications for the Audio: 
-  STK-1120 chipset
-  AC97 interface which supports an external 16 bit AC97 codec 
-  at 48k/per second sampling rate and 2 audio channels
-  Audio pipe can transfer 192kB/sec
-  USB audio class compliant
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