No, that's not what I mean. All of the inputs I mentioned are analog inputs and outputs. USB is digital.

You have two options for connecting the 4600.

METHOD 1: Connect a cable from either the "Tape Outs" RCA jacks on the top panel or the "Main Outputs" XLR outputs on the rear panel to the input jacks on the MDX 4600. Connect the output jacks on the MDX 4600 to the input jacks on the external recorder or to the analog sound card inputs on the computer. You don't need an external recorder.

METHOD 2: A second way to use the MDX 4600 is to connect the jacks of the ALT 3-4 outputs on the rear of the mixer to the input jacks on the MDX 4600. Connect the ouput jacks of the MDX 4600 to a line input on the mixer, such as Line 7-8. You must then press the ALT 3-4 mix on each channel that you want to go through the compressor. The signal going through the compressor will come back into the Main Mix through Channel 7-8. The benefit of this method is that you can hear the output of the MDX 4600 in your headphones. Method 1 does not allow you to do that. The disadvantage of this method is that it is more complicated.

Both of these methods are covered in the manual. As far as I know, I have described the process as clearly as I know how to describe it. Therefore, I have said all that I can say. Read the manually carefully - multiple times - and then figure it out. It's not that hard.

All that being said, I don't like or use the MDX 4600. The Behringer mixer has compressors built into channels one through four. If you want to mess up your audio with a compressor, why not just use those and save money?

Good luck.