Problem switching from FA-66 to FA-101

Hi there!

I recently bought a FA-101 to replace my now three years old FA-66 in hopes to get the same sound quality and ease of use (which I honestly love from my FA-66) just with more connectors, but I was really disappointed. The sound quality from the front connectors is really terrible compared to the FA-66, it is much more noisy and it is not an "analog" noise but rather a digital-sounding distortion like reducing the bit rate. I used the same instrument/input gain/recording setup for both interfaces and it is a clearly audible difference between those two, even just by monitoring, without recording. Is there a possibility that my FA-101 has a broken A/D converter (I ask this because sound from the digital in sounds perfectly clean to me) or may there be other reasons for this behavior? I never used the limiter of the FA-66 so it can't be that one. Thanks in advance for any help on this. I am also willing to post some recorded examples here if you wish.

Kindest regards,

— Daniel