I recently purchased 2 new 0-4-2 Porters with sound & a 2-6-6-2 Mallet along with sound. The Mallet sounds absolutely spot on just like the rest of Bachmann's sound equipped lokies, but the porters have a tendency to to make crackling sounds when multiple sound effects are played together. (Ex: Chuffing, brake squeal, & whistle.) Does anybody know if this is a problem with the sound exciter(s) or should I purchase a DCC system that can toggle the volume settings of my engines? Any replies are much appreciated!