Hi Just19, I created a 42-madfuload.rules and put it into /lib/udev/rules.d. Then check lsusb via terminal. Now the DFU is disappeared. What should I do now? I pick hardware - sound configuration via Administration Centre and choose snd_usb_audio[AlSA], then click 'advance' and I don't know which driver I had to choose. Please advise. Thanks
Wow! It worked!

It would appear so that installing the madfu-firmware package does not set up a suitable rule for hotplugging the device!
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For the present I would not change the driver.
What happens now depends on what sound control system you are using, and if you wish to be able to use both the USB sound device and also any other sound device - onboard or pci card etc.
If you are using Pulse Audio, then you have the facility to direct any sound stream to any of your sound devices, at will.
If not then you will either
disable the onboard sound in BIOS if you no longer wish to use it
or
have to get the hardware location of the USB device and direct the sound stream to it.
In a terminal
aplay -lwill list all the player devices attached to the system, while
arecord -lwill list all the input devices.
You should be able to use that info to send a sound stream to the USB device or to record from its input.
I find that Pulse Audio is the easiest to manage. Before it was available I had great trouble controlling where the sound stream was sent, because the device location changed at each boot or plug in.
Pulse overcomes that, allowing complete user control.
Of course if you are disabling all other sound devices then the system will use the only one it sees.
I must bow out until tomorrow at least.
Almost 3am here and past my bedtime

Good luck with the rest of the setup.
regards.