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Debugging problems with USB 2 Audio Class operation

If you are having problems with you USB audio device, please first try connecting to a different USB port - and a different USB Cable.
Really, please do this. I've spent time with multiple customers who insisted that they tried all of the USB ports on their computers with no improvements - and then they later told me that they finally found the solution when they connected to the other USB port!

This is a common solution because - especially for laptops. Often there are built-in USB devices that share the USB root hub with one of the external USB connectors. This can be any number of peripherals: keyboard, mouse, bluetooth, wifi, camera, battery management, any other proprietary computer management hardware. Many root hubs are not capable of multiplexing devices so as to guarantee Audio Class throughput. Because of this, it's well understood and documented for most USB2 Audio Class devices that root-hub sharing is not supported. You can access info about your computer's various USB controllers, root hubs and devices in your Control Panel/System/Device Manager and determine whether your USB port is sharing the root hub with another device. If you hear ticking when you move your mouse - that is a good clue.

Some customers with problem USB ports have resorted to buying Thunderbolt or PCIE - to - USB adapter devices. I believe that there are some USB ports in computers that have bugs - that do not correctly support USB 2 audio class.

Try a different USB cable. Sometimes they are defective. Don't use a long USB cable or extension cable. This probably won't work well. It's important to understand that, unlike other USB classes (such as mass storage), USB audio class is has no provision for error detection / correction. The host must deliver the correct audio data every 125 microseconds. There is no retry or catchup. This is the way Audio Class is specified by the USB consortium - not our choice. So, no matter how powerful the host computer, if its not guaranteeing throughput, if the data is not on-time every time, there will be interruptions in audio.

USB 3 ports
Grace Design USB audio products work correctly with USB 3 ports. We have encountered some exceptions. It's a real-world reality that not every combination of computer and USB device will be successful but we work very hard to ensure compatibility. It has been documented that some USB3 interfaces and/or their drivers do not fully and correctly support all USB 2 functionality. The m920, m905 and m9XX are not USB3 devices. These devices support the USB consortium's specified Audio Class. This is an industry-wide communication protocol, not invented by Grace Design. There is not a USB3 audio class. My limited understanding is that USB3 is an aggregation of multiple USB2 interfaces. The m920 uses a USB1/2 cable and connects to only 4 pins of the USB 3 host jack so as to access its USB 2 emulation mode. The USB 3 interface has to work correctly as a USB 2 interface. I have read that this is not the case for every USB 3 interface.

The m9XX/m920/m905 worked great until I upgraded my OS.
In some cases, I think this has been the result of bugs in the new OS. Hard to believe? We've had numerous reports like this that were later resolved - a few days later everything started to work correctly again. There are risks to early adoption of the latest OS. I suspect that in some of these cases there were bug-fix automatic updates from the OS provider that eliminated the problems.
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