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[Andras <eandmsz@xxxxxxxxx>]

Same problem here with Intel D54250WYK NUC box + Audiolab M-DAC which
uses async USB connection for 24/96 audio.

It seems that the problem only occurs with Intel USB3 controllers.
Unfortunately the internal USB2.0 headers in my NUC are controlled by the same USB3.0 controller, and there is no option in the BIOS to disable the XHCI (USB3) mode.
I have indicated the problem towards Intel:
https://communities.intel.com/message/255474#255474

Here is a discussion regarding the Linux xhci_hcd isochronous problem:
http://www.spinics.net/lists/linux-usb/msg107264.html

Last mail on 8 May 2014: 
"This does seem to point to an incompatibility between the driver and 
the Intel xHCI hardware.  Figuring out what that incompability is may 
not be easy, though..."

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https://bugs.launchpad.net/bugs/1308628

Title:
  xhci-hda does not support isochronous streaming on usb 2.0 devices

Status in Ubuntu Studio:
  New
Status in “linux-lowlatency” package in Ubuntu:
  Confirmed

Bug description:
  I have a Presonus AudioBox 1818VSL (usb audio interface,) which was
  working flawlessly for about 2 years on ubuntu 12.04. I bought a new
  computer with usb 3 ports and installed 14.04, and suddenly the audio
  is popping and crackling. The computer is loading the 1818vsl as a usb
  3 device using xchi-hda even though it's a usb 2 device and should use
  ehci-hda. From what I understand on this thread, this is a problem
  that affects other usb audio interfaces as well:

  https://forums.presonus.com/posts/list/33427.page

  I found other users in the forums having this problem. Since xchi-hda
  is prebaked into the kernel, the only workarounds are

  1. Disable usb 3 in BIOS or
  2. If you don't have that option in BIOS, compile a new kernel with xchi-hda and ehci-hda enabled as modules and then blacklist xhci-hda.

  These shouldn't be the only options for Ubuntu users!

  My proposal is build xhci-hda as a module in the default Ubuntu kernel
  so that the affected users can blacklist it without having to compile
  an entirely new kernel. There are very few usb 3 devices at the moment
  anyways, and this should have very little effect on performance for
  other users.

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