I just built this VI in 6.1 and figured that the SO Set Num Buffers.vi is not available and therefore you get that kind of clicking sound comparable to the sound in the 7.0 Version when using 0 buffers. Do you know how to fix this?
I'm afraid I've only got access to 7.0 & 7.1. 😞 SO Set Num Buffers.vi uses a Call Library Function node to access lvsound.dll. Hmmm... I've had a scan around and you could try checking this link It may give you some clues.
It seems that the LVSound.dll is compatible from 6.1 to 7.1 so I found the function in the library and built the missing functions according to your example. That seems to work.