Question

how can I connect an external compressor and use it as a Send and return? Are the AUX input and outputs for sends and returns and will this affect all channels?

Answer 1

Check out section 4.6.1.2 "Working with External Effects Processors" in the online manual for the consoles. It goes into detail on how to do this.

https://pae-web.presonusmusic.com/downloads/products/pdf/StudioLive_Series_III_OwnersManual_EN_14052018.pdf

Answer 2

Make sure the Aux channel you are using is set to Analog and not USB in the Fat Channel controls. I think it comes defaulted to USB, but you need it in Analog if you want to hear it's affect through the StudioLive console outside of your DAW. This is not mentioned in the manual.