So Miriam you were asking about practicing things in another thread. Here's a little homework assignment to get you thinking if you are interested. You are operating a very simple sound system with the following equipment. (Nothing particularly special about the equipment itself, it's all pretty basic gear.) Your have two Sure SM58S microphones. You have a Mackie 1202-VLZ3 mixer You have a Mackie FR800 amplifier. You have two Mackie C300z speakers. The system is set up properly, all connections are correct, you test it, and it works. You leave the area for a while and come back before the show starts. The performer picks up the microphone and no sound comes out. By my count there are 14 things that could possibly be wrong. Some are unlikely, but all are possible ways to get no sound out of this system. This is one of my favorite exercises for teaching sound to new students. It's more fun to do in class with the actual equipment. I have the class turn their backs for a bit while I mess with something else then have them figure out what I "broke" this time.