I bought a radio in the US and bought a Step Down Transformer so that it would work here - the following is similar to the one I have:
VOD-100 UK
This voltage converter has been designed for use of 100-120 volt appliances in countries with 200-240 volt current. The product is hardwired with a UK grounded plug. It is rated for a 100 watt capacity.
Step down 100 watt Convertor
For American Product to be used in 220- 240V countries
Whether or not you can use it depends on the appliance.
A transformer will convert the voltage 120v to 230v no problem but will not change the frequency ie US 60 Hertz to Europe 50 Hz. So it depends on whether the appliance is frequency sensitive. e.g. Anything containing a motor is frequency dependent.