Model Railroading > Scaletrains and Kato Sound Box

I recently purchased a pair of Scaletrains N Scale ET44's with DCC w/o sound. I have test run each locomotive separately on my layout which is DC and includes a Kato Sound Box, successfully at barely 1/3 throttle with excellent speed for the setting. However, when I tried to test run the pair together, the Sound Box tripped in apparent overload before even half throttle. Now I have other multi-units trip the Sound Box in overload, but at much higher settings (usually above 80% throttle). Do the Scaletrains units draw that much amperage?