I use VB Virtual Audio Cable - always worked very well for me. Im pretty sure VB will only do stereo (I.e. 2 channels) though. For multichannel (I.e. if you want to send d1, d2 etc to separate channels in your DAW) you'll need a multichannel audio device. Nerds.de (the LoopBe people) make one, it's not free though (but it is cheap)
There is some discussion about this here.