For the UA-2, if you change the sample frequency or
mode, this involves
setting a hardware switch on the device, and then restarting snd-usb-audio
by a 'modprobe snd-usb-audio'.
That's interesting. I usually re-started the device on my FA-101. Maybe
the module auto-loaders triggered by that was what really was necessary,
not the device re-starting. Ah, the joy of knowledge going easy on the
power converters...