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.

For gear that has dual voltage transformers, the alteration requires the re-setting of 4 wires which are usually under screws. Super simple, zero effect to retail value.

Low cost, reliable, high benefit, and now you can use US surge protectors on it. Totally the right way to go.

If this would require a transformer swap, it's usually prohibitively expensive and cumbersome to do, with some risk.  That I would leave alone.

@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.

Anything that plugs into a wall has to have safety information on the back panel. If the unit has, for example, a multiple primary transformer that can accommodate different voltages, then all those voltages will be printed and clearly visible. Usually it's in the form of a list with blank boxes and the unit voltage has a mark on the corresponding box. This is the only way to be sure it's convertible without reconfiguring.

If a tech claims to have experience converting operating voltages on that particular unit -- and the unit only has one voltage printed on the back -- you'll have to use your judgment.