Behringer UFX1204 linux/jackd report.

EDIT: Working solution see    • Behringer UFX1204 one hour run no xru...  

USB: This video demonstrates that i could get this card to work without constant xrun(one audible xrun) every two minutes or five to six minutes depending on jackd parameters. This xrun appears even if no client is connected / nothing is running with both firmwares available from behringer. I tested with fedora 27 on my workstation and ubuntu 16.04 on my laptop both with same xrun problem.
The way i got it to work was using alsa_out as playback device.
Using "jackd -R -P99 -dalsa -dhw:0 -r48000 --p128 -n3 -C -S" for starting jackd as capture only device. -S is optional.
Then i started alsa_out device with "alsa_out -dhw:0 -r48000 -p128 -n3 -c4"

I also tried zita-j2a but it was not stable on my fedora 27 system.

In the video i could run sequencer64 sequencing microbrute, electribe and zynaddsubfx and sending clock to electribe. Then recording hydrogen, zynaddsubfx, electribe(stereo) and microbrute (mono) to ardour and monitoring it throug ufx1204 with DSP load about 20% with no xruns.

Qjackctl shows no xruns and recorded ardour session reports none also. And i could not hear any.

Firewire alsa drivers: Works with no xruns using alsa firewire drivers. Seems that only frame rates 256 and 512 are supported. I was successful with '44100/256/2, 48000/512/2 and 96000/512/2. Jackd would not start with other tested combinations.
Note that DSP load was minimal. See:
   • Behringer UFX1204 firewire linux/jack...  

Firewire FFADO drivers on fedora 27: Could not get this to work and did not bother to get newer ones.

Conclusion: Behringer UFX1204 uses snd_usb_audio module on linux. I think the static xrun problem with usb resides between this module and firmware.
I might be wrong.
Anyway the mixer/audio interface is usable and in use with my setup.