You are correct. the Intel xHCI does not work with USB AC 2.0. This is the root cause and has affected those new products with this USB 3.0 chipset. We are working on the code and have been doing this round the clock. If you PM us with the retailer details we are more than happy for them to extend the period.
We will have the solution but this has not only effected DACs out there but also peripherals such as HDDs and thumb drives.
iFi is in the same boat as the others.
As an interim work around, you can go into the BIOS and reset the port back to USB2.0.
Thanks for the swift post. Much appreciated!
Yes, that's how I'm testing the iDSD atm ... by disabling USB3 support in BIOS. However, MacBook Air (late 2013 Hanswell release) was intended to be primary platform for iDSD, so I believe that there is no workaround at this stage. By the way, is this related to XMOS specifically or just your implementation? (as other DACs tested, namely Audioengine D3 and HRT Microstreamer were perfectly stable).