Help with effects loop/patching in a mixer

I have a few synths/sound sources that I plug into a small Behringer mixer, I use the effects loop (aux send/returns) to be able to use my effects on certain sources at certain times. I find that the effects (strymon DIG and bluesky) do not sound as nice using this method as they would if I were to plug a sound source directly into them. Does anyone know of a mixer (or other system) I can use that will make my effects sound as good as they would when plugged directly in? or does anyone know of a way to make it so my Behringer mixer can do the trick? its a xenyx 802 mixer.