@Wolf...there's always a first time. @Smoffat if I get a chance I will talk to the factory about the CL-120/KT-120 issue and see what they say. I can tell you that the CL-120 has triode configured output tubes. The Ref 150 has a different tube compliment and does not run the output tubes in triode. I believe it runs the outputs in ultra linear configuration so it will sound different. Also, the CL-120 uses servos to set bias on half the output tubes and the cage must be removed in order to set bias. The Ref 150, I believe, allows user adjustment without going inside the amp.