PreSonus does not officially support any SD cards larger than 32GB because they would have to be SDXC. The SD card reader only does SDHC. The best cards to buy are Samsung and Sandisk Class 10 U3. You will get the most consistent results from those brands. Other brands claim to be built to the same spec but when you do a speed test on the mixer, they can't handle the full 34 channels of recording.