I am confused about how my RealTek ALC 650 (onboard) sound card always upmixes 2ch stereo to 5.1 in DirectSound mode (WinXP). It is very easy to test in foobar: in WavOut, I always get 2ch stereo. With DirectSound output, allow h/w mix results in 2->5.1 upmix, which I do not want for music, disable hw mix, everything is fine. In players where I can not enable or disable hw mix, I always get 5.1, unless I select wavout, which some players won't even allow me to.

The only option I have is in the soundcard driver setup, select 2 speakers when I want music, and 5.1 for movies. Why can I not have the driver and card simply pass through the number of channels unaffected? I can always use Matrix Mixer for surround content I want to have upmixed...

Does anyone know if this a DirectSound feature, or a driver feature? I notice the same problem with a Hercules card. Do some 5.1 cards offer an option to not always upmix in DirectSound mode?