recording sound problem with new mac pro

[BRAMI serge]

Well hello everybody 
I need help 
I use LC for my professional use 
I have the following problem

from 
LC 6.7 … the recording sound doesnt work on my MAC pro ( the new one)  and only on this mac 
LC 7 and 8 recording sound  it is the same thing

on my others computers  IMAC and mac book air recording works fine  this with exactly the same stack (which is shared by dropbox)

quicktime player recording works well on each computer 

dontuseQT  is set to false


the recording input for the mac pro  is set to the APPLE THUNDERBOLT  DISPLAY mic   in the system preferences

the recording input in the script is st to "dfilt «   but i have tried with other options (imic emic …) and it doesnt work


it is a big problem for me , It prevent me to upgrade to the newest version of LC

any idea ??

best regards