What I would like to do is to pass an arbitrary audio file to a DirectShow filtergraph and receive a (PCM audio) stream object in the end using .NET 3.5 C# and DirectShow.NE
This (AVILibrary Wrapper) may lead you to a solution, it's not DirectSound based (which I get the feeling is very much biased to interfacing your code with the playback hardware) but could be the answer.