For a stereo compressor you need 2x analog IN and OUT, right?
And for a preamp 1-2x analog input (depending on whether it is mono or stereo).
If you connected already your active monitors to the analog out of your AIO Pro .. well .. whats left then in terms of analog ports? If I see it right only 2 analog inputs for connecting e.g. the preamp.
To connect the compressor use ports of the ADA8200 because the AIO Pro has no other 2x analog I/O in/out than that.
Or digital, but I assume your compressor has only analog I/O, no AES or coax. SPDIF.
You will need the optional D-sub Breakout cable for connecting them balanced using XLR cables.
For connecting two channels you have also digital inputs and outputs (AES, coax SPDIF).
But it is rather unusual that 1-2 ch preamps or 2ch compressor have such digital I/O.
BR Ramses - UFX III, 12Mic, XTC, M-1620 Pro D, RayDAT, ADI-2 Pro FS R BE, X10SRi-F, E5-1680v4, Win10