This applies to the Scarlett 2i4
If you're using the unbalanced (RCA) line outputs to send audio to an external mixer from your Scarlett 2i4 and you notice that outputs 3 & 4 are louder than outputs 1 & 2 then this may be due to the position of the monitor dial on the front of your 2i4.
The volume for both balanced and unbalanced outputs 1 & 2 are controlled by the monitor dial on the front of your 2i4. Therefore if you're experiencing less signal from outputs 1 & 2 than 3 & 4, make sure that your monitor volume is set to maximum to ensure that both sets of unbalanced outputs are sending equal volume levels to the two channels on your external mixer.
This is essential when using your 2i4 for DJ'ing as having unequal input volumes could cause uneven levels when crossfading from track to track.