Probably it requires non-free firmware and that's the reason why it doesn't
work. Try using a search engine to find more about that particular hardware.
Searx instances are very good for instance -> http://stats.searx.oe5tpo.com/
Gives me among other things this page ->
http://libremusicproduction.com/tutorials/setting-and-using-terratec-dmx-6fire-usb-external-soundcard
I did not read that page and have no idea if it recommends any non-free
software. We are against proprietary software of any kind and do not support
it here. If that's the case you are on your own..
