Summing using MR816csx

Hello folks I am doing summing using my TLaudio Fat track and MR816csx
I plugged the channel In (1/2) to recording and it was sounding
I little opaque comparing to original signal, so I tried using Insert unbalanced to do this and to my surprise the Print sounds much better than balanced (1/2)

Why this happen?
Is it because I’m not using Pre amp ?
it even the signal unbalanced it’s sounds better ?