RTL-SDR enthusiasts who use Windows are familiar with the need for a virtual audio device to connect the SDR output to decoder programs such as dsd. The hangup is that you need to purchase Virtual Audio Cable software to the tune of $25 (more than the cost of the SDR dongle itself.)
Now there’s a donationware alternative to VAC for Windows known as VB-Audio software. VB-Audio installs drivers on your Windows box giving you a VB-Audio cable choice among you audio devices. This allows you to pipe the SDR output to the decoding program of your choice for free. Of course, the VB-Audio developers appreciate a donation, and in exchange for a donation of any amount you get the ability to unlock two additional virtual audio devices, helpful if you’re using a multiple-SDR setup.