Hi, I'm having a petty argument w/ a tech support person and want to get my facts straight. Please help if you know the answers to these questions. I put this in amps because this is where most of the tech people seem to be. What is the difference between voltage and amperage? Will adapters whose voltage is too high *safely* power lower voltage devices? (18v wart for 9v pedal)? What are the equations for power? Watts = ? volts = ? amperage = ? Thanks!