Thanks for the info guys. I'll pass it on. My friend sent his P7 to Dallas for a P9 motor and MU metal shield upgrade so I'm interested to see if that attenuates the hum. From what I have read here it sounds like it might be good to change to a MC too. Since he just bought the unit with a new Exact, I figure he'll run it as is for a while. This brings up a question- Can the shield be added to other models or is it only possible on the P7? Anyone try this?