Sure. 12 volt battery (car battery through cigarette lighter plug) is the source for a powered speaker set up (computer speakers) as well as the Empeg. They are both getting power from a common ground point and 12 volt connection. A powered (active speaker system) should not be an issue as that's essentially what's in a car anyway when you have speakers and amps, I just don't have a way to test it like that.

I was just thinking something like age might be a factor. I originally thought ground loop too but everything that can be made common power wise already has been. I will go ahead and recheck signal grounds.

Thanks!