Elizabeth - 99.9% of power conditioners are not isolation transformers. Only an isolation transformer can separate the ground connections and eliminate ground-loops. Even this is not optimum. Better to have isolation at each component.
Conditioners are great at preventing noise from switching supplies from getting back into the power line or preventing damage from lightning strikes, but that is about it. I don't like them for the most part. Never use them.
Steve N.
Empirical Audio