The conventional wisdom is that it will affect sound. I don't notice any degredation myself; however, I haven't done any critical comparisons. If it does affect the sound slightly, it doesn't seem to take away from my enjoyment of the music. And I don't want to take the risk of not using one. One time during an electrical storm, there was a power surge which took out the protector. That was enough to convince me that it was a good investment. Now when I hear thunder, I don't even take the risk that the protector will be sufficient. Everything valuable gets unplugged from the wall, which is what most manufacturers of electronic equipment will suggest anyway.
