USB Bulk mode

Today almost all USB audio is UAC2 (USB Audio Class 2).
In those early days of USB audio, some manufacturers didn't use UAC1 but developed their own solution.
Instead of the isochronous mode, they used bulk mode.
Bulk mode is asynchronous by design.
As it is bulk mode,
• No guarantee of bandwidth or minimum latency
• Error detection via CRC, with guarantee of delivery.
Isochronous mode is exactly the reverse.

It is not trivial to develop a driver.
You have to do so for each OS supported and check its working for each update of the OS.
In practice it often turned out to be a very buggy road.
Today almost all audio brands buy a USB receiver from a specialist.

More technical information about USB audio can be found here.