When you "noisy" do you mean "hum" or "hiss" ?
Just as a test, try lifting the ground plug on your preamp power cord. Use one of those cheater plugs that will allow you to use a two prong socket. If the noise goes away, you are probably looking at a ground loop. If it does eliminate your problem, "don't continue using it this way. It is not safe but it will tell you if you have a ground loop problem.
On another note, most transformers allow for 110 and 220v connections. Did you ask the manufacturer? If not you could have the transformer changed to a 110v transformer. Step-up and step-down transformers tend to cause some issues.