With traditional electric guitar amps, you need a transformer if the device is to be operated in different countries with different mains voltages.

This is not necessary with the AMP1. A modern switched-mode power supply constantly supplies the amp with all internally required operating voltages, regardless of the mains input voltage. As a result, AMP1 delivers exactly the same sound and performance anywhere in the world without additional adjustments. You only need a power cord with the country-specific power plug.