VirtualBox. Latest version. I did download the latest zadig drivers. The R820T came up as a Realtek device. I'm using SDR#, but doesn't matter since there's no RTL-SDR/USB seen by Windows.
Same results. I think that Virtualbox just doesn't do a good job with audio.Lower the sample rate of the rtl in sdr sharp click on the gear icon on the top left. Lower it to about 1 mhz