[DawnOfDoom]

Ok I've been seeing this kinda stuff alot on youtube in videos that go through a guitarists setup and it has this box on top of their Amp head and cabinet with these extra panels in it like in this picture http://images.macworld.com/images/ne...y_revalver.jpg

Im just curious what do these things do? How are they set up? Is the amp head's line out go into them and then their all stringed together and then the final out goes to the cabinet?

Sorry for all the questions