You can passivley split line level 2-3 times without issue as long as you don't have stupid long cable runs and are using equipment made after ~1970. This is done in every pro studio all the time. Every patch bay has "mults" as in multiples. It's just jacks normaled together to split signals.
This works because they are fairly large signals with low output impedance and very high input z.
This results in very little extra current being pulled from the output to feed two or more inputs.
Ohms law, no change in current, no change in voltage, no drop in signal level.
You do need a proper grounding scheme in your gear(everything to one central ground/star ground).