Russell Coker said,

Is there a way that I can reserve device 0 for the USB device? It needs to be reserved because the motherboard hardware is detected before the USB bus is scanned - if the monitor is even turned on when the system is booted.

In theory one can cause ALSA to allocate snd devices to a particular alsa sound device number, I have though NEVER though in a good number of years been able to get this to work with any kind of relaibilty.

Is there a way I can make the system just ignore the motherboard device and have only 1 ALSA card? There's only one thing that can ever be useful so it seems best to make it the only recognised card in the system.

There are two ways one can compile a kernel with only the sound device driver required present. The second method is simpler than anything else and does work. Do an lsmod and identify the main module that is loaded for the offending device then blacklist this module in .... /etc/modprobe.d/alsa-base-blacklist.conf (in debian anyway) This prevents the kernel loading the module. Lindsay