Forgot to mention - before I got the conditioner, I had a very slight buzz coming from my speakers when nothing was playing and the volume was a little higher than normal. Furman got rid of it - that was my original reason for the purchase. It has shut off when the power has gone out (obviously). Not sure about lightning strikes, but something did go in my amp when there was an electrical storm (I wasn't home so don't know if there was a direct strike). I didn't notice any sound difference in my system, but my ears are not as good/sensitive as some of the contributors I am sure.