Converting from 230v to 110 v

I run a euro amp on US 230V (stoves, dryers, ovens etc are wired for 230V).

Using a transformer can be more of an issue.  They can hum.  You should buy one that is quite oversized to support any amp power requirements.  I'd get at least 1KW, if not 2.  

But I found that with an adequate sized transformer, you can do it.  Sound quality might even be better since 230V requires only 1/2 the current.

There is technically a difference between US 230 and EU 230.  In europe one of the legs is 0v to ground.  and one is 230V to ground.  Here in the US both legs are 115 to ground.  This shouldn't be a problem for your amp unless it trips a safety device.  In that case, you might have to disable it.  Most amps don't have such circuitry.    

Jerry

This is a very low wattage situation, any number of inexpensive step down transformers should work fine for you. Just check to make sure your step down transformer wattage is greater than the CD player.

I agree with Eric.  I answered for an amp, which is much more challenging service.