On the ‘CS’ unit, the line in is balanced and that’s the cleanest path to use as an input. The insert point is unbalanced and does by-pass the input stage, but there’s no real advantage as, with the gain set to unity the input stage is transparent. 
On the ‘CS’ unit, the line in is balanced and that’s the cleanest path to use as an input. The insert point is unbalanced and does by-pass the input stage, but there’s no real advantage as, with the gain set to unity the input stage is transparent.