I was wondering if the card readers in the X5 will have some future proofing, and be able to work with cards of larger capacities. That is as they come available. The Ibasso DX50 is believed to offer that feature. But a double reader with that feature would be double the benefit.
Okay, it is a bit more complicated so bear with me here. SDXC comes in two standards: the current one we are using is the 3.0 version that also define SDHC. With 3.0 standard, SDHC and SDXC have the same pins configuration and power requirement. The difference is, SDHC uses FAT32 for formatting while SDXC uses exFAT. However, FAT32 supports up to 2TB, same as exFAT, so you can format a SDXC card with FAT32 and the SD reader itself should not know the difference. However, exFAT is a Microsoft thing so if you plug a FAT32 formatted SDXC card into a Windows PC, it will always ask you to reformat it back to exFAT - this is Microsoft way of trying to trick people to stick to exFAT. With a compatible card reader however (like the one inside X3), even a Windows PC will allow read/write on FAT32 formatted SDXC card. So in theory, X3 should support up to 2TB of SDXC card, right? Well, not so fast.
At current stage, the reading/writing speed of v3 standard is enough (SD is max'ed around 256GB while microSD is max'ed around 64GB). But once we move toward 1TB and 2TB, the reading/writing speed will likely not be fast enough. To solve this, the version 4.0 will replace the current version 3 standard. With version 4 card, it will requires extra pins and different power requirement. V4 card reader will be backward compatible to V3 card, but the V4 card will not work on V3 reader. So the simple truth is, though iBasso claims the DX50 is future proof, it really isn't - if the future 2TG SDXC card is V4 standard, neither DX50 or X3 will be able to read it. At this point, no one really know when V4 standard will be used, so claiming future compatibility is mostly just a wishful thinking.