I worked perfectly Jeffro solution, thank you very much! I mention my step by step: 1.- Download and install the most current driver for the Fast Track C400 (
http://avid.force.com/pkb/articles/d...k-C400-Drivers). 2.- At the end of the installation DO NOT RESTART. 3.- Apply Jeffro's solution (Deleting the M-AudioFastTrackC400.kext from System> Library> Extensions (leaving it in Library> Extensions) should eliminate the crash and allow the C400 to be selected in AMS or Sound 4.- Double Check that effectively delete the above mentioned file and leave the one I should leave 5.- I went to System Preferences and saw that the Driver was already installed 6.- Restart the computer 7.- When fully loading the operating system, connect the Fast Track C400 and everything worked perfectly.
My iMac came with the High Sierra already installed and it is impossible to do the Downgrade for what I was looking for a quick solution for this Driver, because the first time I installed it in this OS, the OS collapsed and did not allow the computer to boot. I had to reinstall the OS again.
I hope it works for everyone and that very soon AVID will update the Driver for macOS High Sierra 10.13. I hope so. And again, thank you very much Jeffro.