My son received a HO scale Bachmann DCC commander set with the Union Pacific GP40 DCC locomotive for Christmas. From 1st use, the loco has made a fairly load buzzing/humming sound (much like a noisy transformer) when power is applied. Our Hobby shop ordered a replacement GP40, but it was actually noisier, so we kept the original. My son has a Bachmann DC SD40-2 (which we run simutaneously on channel 10) which is very quiet and produces little to no noise, especially compared to the GP40. Is this normal for Bachmann DCC locomotives? My son would like to buy one more DCC loco, but I'm hesitant to let him purchase another Bachmann.

Thanks,

Darp