All the 16-bit family sound cards including the SB16, SB AWE32 and Phone Blaster have one 16-bit and one 8-bit DMA channel. It is possible to make use of both DMA channels to create full duplex applications.
Each of the DMA channel can be programmed to perform either wave recording or playback. However, if one of the channel is being used for recording, the other channel must be used for playback. For example, if the 16-bit channel is used for recording, then the 8-bit channel must be used for playback.
In addition, the other restrictions are:
You can download Windows example here.
You can download DOS example here.