Let's take case of this mixer.
You put bal. audio sig. to say 2141 then go to pre-fader aux pot
and from same point to fader; now, you want some level after "0"
in fader and post-fader aux; in passive terms it is not very possible
due to leakage stuff (impedanse after fader is not 0 ohms) and level falls at fader's "0" point ; then you boost after fader with usual opamp
connected as non-inv amp gain 6-10 db (this is yout "in-hand-gain),
than you go to anpot and after papot to mute circuit and then buss resistors....classic and simple;
sound qality is good designed pcb's, clean enuff power supply and good parts...