what size of wire is required for 18 W USB-A?

Actually this is a cable question. I see wall warts out there advertising 18 watts.

  • 3A USB Type-A & USB Type-C Wall Charger
  • The spec says “Output Voltage- 1 x USB Type-A 18 W”

I thought the USB-A spec was limited to 3 amps therefore 15 watts but, my question is about the wire. Can any old USB-A to USB-mini handle 15 to 18 watts? — USB mini: the small trapezoid shaped plug that came with every chargeable device you bought 10-15 years ago.

I’m wondering about powering small audio amplifiers. Probably rarely reaches max power consumption but, will be continuous running. And 5 volt works as I tried it with old lesser amperage warts.

TIA