I used to use the EI 12AX7 tubes. They were a great tube;I loved the sound. They were my favorite current production 12AX7 until they started developing problems with microphonics. In my experience, 80% of the tubes went bad within 2 to 3 months of use. EI started putting out an "Elite" version of the tube, but they eventually developed microphonics as well. Did EI ever correct the problems with their tubes? Has anyone used any of their recent production tubes? I'd like to purchase some more 12AX7's, but not if the reject rate is still high.