[Edit: I confirmed that SDL defaults to directx video and audio. Therefore, the only advantage of the attached builds is that a directx6 function is available. However, the single directx6 function is not used by dosbox. Therefore, the attached files probably won't be of use. I left the prior message below.]

The SDL library has a choice of Windows audio devices: dsound or waveout. Dsound refers to the DirectX sound component. To enable the DirectX sound functionality, the SDL library must be compiled with specific DirectX header files.

I compiled three versions of SDL.dll (attached files). One is for WaveOut. The other two SDL.dll files are dsound capable. One has the typical DirectX5 sound while the other has an additional DirectX6 sound function.