a double bus design?
I had not heard that term used together with USB.
As I understand how USB works, I think the answer would be no. It's an advanced single bus design.
There are some features that would help a USB audio device do some near-real time work though.
I've used this USB interface tutorial covering basic fundamentals for a couple yearshttp://www.eeherald.com/section/design-guide/esmod14.html
I think this is the part of most interest to you (about half down down the wall of text):USB can support four data transfer types or transfer mode, which are listed below.
Control transfers exchange configuration, setup and command information between the device and the host. The host can also send commands or query parameters with control packets.
--> Isochronous transfer is used by time critical, streaming device such as speakers and video cameras. It is time sensitive information so, within limitations, it has guaranteed access to the USB bus. Data streams between the device and the host in real-time, and so there will not be any error correction.