I'm using a microSD card formatted ExFat, on OS X Yosemite, and was able to load files onto it which played on the Pono. However, when I tried to backup the microSD card included with my Pono (Tom Petty LE), my Mac did not recognize the card (still working on trying to get PMW to transfer files from my Mac to the Pono player). Does anyone know what format the cards are that Pono uses? Is there a list of what SD card formats the Pono player supports?