I have an inertia type (DC) power supply which is now approx 15 years old, it still works and until recently been very happy with it. I have just set up a small oval as a test track with a cheap $15 power supply. With the inertia power controller i get a buzzing sound from the loco as soon as i turn the power on which increases as the power increases, with the cheap controller no noise at all. Unsure if the buzzing has always been there or that i have become accustomed to it. WHAT IS HAPPENING? DO I HAVE A PROBLEM?