Connecting multiple audio sources

Hi!

Bought myself the MF4, since I’ve wanted to connect multiple audio sources to one Interface and control everything on my daily main system (PC-1).

So I have Edifier MR4s connected to the L/R output via 6.3mm, and PC-2/PC-3 from the onboard 3.5mm to the back panel input 3 and 4, over a 3.5mm to 6.3mm cable.

Now the main system (PC-1) output sounds perfectly fine, love it, but the output from PC-2/PC-3 sounds not as it should be, muffled, like underwater and no depth. Any thoughts?

-I’ll try to update with a video link, when I get the time-