It is important to determine which line level is appropriate for you studio equipment. Setting the +4 or 10 dBu operating levels help determine the input and outputs loads a particular piece of equipment can handle or deliver. +4 dBu is generally considered "professional" and 10 dBu "consumer". Some processors, etc. can be toggled manually between +4 and 10 dBu via an external switch or internal jumper (such as the 888/24). However, many are permanently set. Check the owner's manual for you mixer, amplifiers, or effects processors to determine the correct operating level for you studio's equipment.