HELP with MAC MINI and PS DIgital III DAC

How are the two being connected?

First thing to check for -- if you are connecting the Mac Mini to the PS Audio by USB cable, has the Mac Mini recognized the additional output and have you selected it as your audio output on the Mac? Open System Preferences, select "Sound", and click on the "Output" button to view the selected and available outputs. Your DAC should be one of the available outputs. If it is not already selected, do so, and see if that works. If you don't see the DAC listed as an output, check to make sure your connections are all solidly seated (it's easy to fail to fully insert a USB plug).

Meiwan raises a good point/possibility...Itunes cannot handle FLAC...I use Max to convert from FLAC to AppleLossless, and it's free and easy to use. Once you convert to Alossless, ITUNES will see and process it just like other music in your library....

AMARRA, while great stuff, is only a front end...and works with ITUNES

HOWEVER, you really need to tell us what you mean by "can't play"

Without knowing where you are stuck...it's hard to for us to tell and help you.

K. Thanks to all- using USB cable to DAC. Thinking that is problem. High res transfer not happening. Amarra software says can not accept file , then shows 9600 not ok? Read somewhere need to use digital link instead of USB ? But why Rad shack working fine ? Also,PS DAC "upsamples"? So is it not set up to "just play" hi res?

Oh, and Amarra has built in Flac converter thingy to make new iTunes readable files. Hav done this. They will play thru iTunes only. Not thru Amarra. And play at 42(?) vs 96(?) that I prefer and had BEfoRe upgrade?!?