Hi, I have found an original RM 9 with EL34 tubes. In speaking with the owner who was straight forward with me he told me the unit has a hum audible at the unit to about 2 feet away. He states that it does not go thru to the speakers or affect the sound. He further states that he was told this was common with the RM9's. George, do you or anyone else have any thoughts about this. Any help would be greatly appreciated. Thanks Richard