I don't see why not. 18 gauge ought to handle 7 amps with no problems, plenty for just about any function in building guitar amps. And silver plated! Wow, that's special . . . should attract the attention of those seeking boo-teeki qualities. It's copper in the middle, right? So you have the same temp specs as any copper wire. Melts at 1950 degrees Fahrenheit. Again plenty of margin in any guitar amp. Voltage? As bus wire, has no insulation, right? So make sure there's enough space between your wire and any high voltage node so you don't tempt an arc to form. Overall, I don't see any problem.