POLL About Voltage Change on Audio Equipment

You’d best talk to someone very familiar with the specific equipment as well as European vs American house wiring. The U.S. gets 240 volts by taking two 120 volt out-of-phase lines, so the 240 volts comes from a hot-to-hot connection.

Europe gets their 230 volts from a hot-to-ground connection.

There is also the 60 Hz (US) vs 50 Hz (Europe) issue which can affect the internal temp of unit and would also affect the speed of some motors.

Depending on the internal wiring of the item, using it on a 240 volt American outlet could reult in a shock or fire hazard, or destroy the item. In short, this approach is generally not recommended.

Another option for you besides replacing the transformer inside the unit is to use an external 120 volt to 240 volt converter. This will maintain the correct hot-to-ground wiring. However, you’d still want to run this by the manufacturer to get their opinion. No one wants to hear about your electrocution or house fire on the local news.

@erik_squires makes a good point. There is some equipment on the market that is built with dual-voltage transformers and can be easily adjusted for use in either the US or Europe.  (Further clarification, none of these comments apply to equipment -- like your cell phone for example, that uses a digital power supply that automatically adjusts to whatever voltage it's plugged in to.)

However, my original comment applies to equipment that was manufactured with a transformer that only accepts one mains voltage.

The OP's original post did not disclose the make & model of the power amp involved so there is no way to offer any comment as to which category this amp falls in.