What is the power loss for a 20 amp circuit over 150' of 12/3? (There's got to be a table somewhere...)
The "problem" is that you are dealing with a dynamic signal, NOT lights or heaters or fans.
The actual current draw will vary with the music, how loud the players are, dynamic range of the music etc.
Yes, the backline will draw some idle current, tha is easy enough to figure out IF you know the specific gear being used.
But the music signal current draw will be constantly changing, so much harder to figure out.
It also depends on the particular breaker being used, how often it has been tripped already etc. Some trip faster, earlier than others.
YES, it gets very complicated when you try to get specific.
NOW, lets just make it a bit more complicated.
YOUR cable is 150' 12ga. How long and what gauge is the cable from the breaker to the outlet you are plugging into?
THAT is the total length of the cable over which there will be loss, NOT just your final piece--------------
Fun isn't it