is there any normal usb 5.1 surround card for mac mini

The HDMI port supports multichannel audio. So, if your AV receiver has HDMI in, you're set.

You can also connect Dolby, DTS and PCM multichannel

via optical. The headphone/line out is also an optical

port. You just need a cable with the mini plug at one end

and Toslink at the other. However, for PCM you will be

limited to 48 kHz, 16 bit 5.1. This is a limitation of the

Toslink/optical standard.

With HDMI you can get upto 192 kHz, 24 bit 7.1. It seems

however OSX limits the Mini to 96 kHz. A Windows install

via Bootcamp will give the full 192 kHz, 24 bit 7.1.

woodmeister50 wrote:

You can also connect Dolby, DTS and PCM multichannel

via optical.

Please excuse, but where do you see this in the specs? For HDMI it's clearly stated, for optical I can't find it on Apple's pages, and I only read people here reporting that it doesn't work. Or am I mixing something up?

Aaaaaaah, while continuing to search I found it at the bottom of the table here!!!!

Mea culpa! 😊