I bought a PGX24/SM58-H6 and registered it on line on 2/22/2011.There is a hum coming from the Shure wireless microphone, I finally traced it down to the DC power supply adapter PS21US. I had an old Shure Mic and if I use that old power supply adapter, the hum is gone.I faxed Shure about the problem but they will not sent me a new DC power supply adapter and wanted me to send back the power supply with the "hum" first to check it out. Shure will not pay for the postage.The problem is:- a 12 volt power supply adapter costs less than $10 and if I have to spend over $5 to mail it, it just does not make sense.Right now to get the two wireless mics working, I am borrowing a 12V power supply from my hard drive. So my hard drive cannot work when I am using the two Shure microphones.If it were not the bad Shure warrenty, I would have given the product a 5 star rating.(P.S. I had worked as an audio engineer before that's why I can debug the "hum" problem.