A surge filter is OK to have between a power amp and the wall outlet. A power line FILTER, such as the TrippLite "Isobar" that has inductors, capacitors etc in-line with the AC is not a good idea because these components have a finite amount of current they can handle. By contrast, a surge protector is nothing more than a MOV across the power line which consumes no power, and is not in series with the AC current. It's only function is to protect from over-voltages which can be very costly for equipment. Of course, the best way to protect against lightning etc. is simply to unplug your components