• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Slight hum from my new soldering station.

I just purchased a new soldering station (Xytronic 137 ESD) after growing tired of Radio Shack's slow responding entry level soldering iron. I'm impressed with this unit so far (it ought to be considering the price). However, there is a slight hum audible from the main body within 6 inches from it. Is it normal?