Step-up/down transformers degrade performance?


I live in London & want to buy American gear. Problem is current here is 240V. I've been advised to buy step-up transformers to attach to the units.
Has anyone any experience with these & how they affect performance of components (esp. CD players).
Would be grateful for any advise.
shabbir
Thanx all for your responses. I'm keen on buying hi-end Classe equipt (esp Classe CDP1) from USA/Canada from Audiogon but haven't found a London hifi dealer who will do the conversion - it's apparently quite difficult.
Will look into the suggestions made & will report back in due course.
hi
speak to customerservice at classe
they told me that their gear is 220vac compatible.
they are very helpful
In these days of the global economy most electronic equipments have power transformers with windings for 120 and 240 volts (sometimes more). Some equipment already has both windings connected, with a selector switch to be set according to where you live. If there is no switch, it's easy to disconnect the 120V winding wire and connect the 240V wire. The power cord wall plug will also need replacement to fit the 240V socket.
As to sound degradation due to transformers...I hate to tell you how many transformers your power has already been through before it gets to your house. Transformers are not evil! (except in the audio signal path). A 240V to 120V step down transformer adequate for high power amplifiers will be big, heavy, ugly, heat-producing, and not cheap. That's why it would be best to use any 240V capability that the equipment already has built in.
By the way, we have 240V here in the good old USA...that's what your stove, clothes dryer, well pump, air conditioner, etc runs on. Instead of buying power line conditioners, perhaps we should all be wiring up our audio equipment at 240V.