I have only just found time to check the differential line drivers cards. They are way off !!

I have clipping on one side.

I have measured after the DC blocking caps between the biased buffer op amp and the line driver IC ( That 1606 ) 

I think I need to check what's happening before the blocking caps now and try and figure out why the output of the buffer opamp is 1.25V peek on one rail and clipping at 1V on the other !