hello there! I have two basses that i want to use live: 1) warwick rockbass streamer 2) Music Drive (Beatiful guitars that no one seems to know about?!?!) The difference between the output of these two is ridiculous (both passive). In my effects board I have a boss geb-7 which as i am sure you know has a volume slider on it. I want to mark it with 2 dots so when i change bass i can simply move the slider. Can anyone suggest an accurate way to measure the volume other than by ear?