I have had this Art Pro Channel in my studio for years now and I would like to breath some new life into it. I ordered and installed Ei 12AX7 Elites and TungSol 12AX7 [ NEW PRODUCTION] tubes only to find that both had issues. The Ei's had +17 dB noisefloor over baseline factory tube. The TungSol tube has a bad harmonic distortion at about 300hz. I like the sound of the Ei (noted as Telefunken like) but needless to say without the unwanted side effects. Does anyone here have any knowledge of tubes and this gear that could help. I am new to tube personalities and need to know info. Any and all help would be appreciated. NOTE: I understand this is not the PRE of choice but I have need and soon.