Thats not surprising. In the pro audio world the nos jan (Joint Army Navy) tubes from the old days are the ones to have clearly. I got the impression that the only use for these type of miniaturized tubes was for military applications . Bigger tubes are much easier to manufacture and therefore cheaper . One reason why I'm surprised the Telefunken's are not better performers is tele was a military industrial contractor for Germany. Their larger tubes are highly sought after and huge money for the right low noise variants. I'm just getting to know the cdm so its nice to have some feedback on the tube rolling . User Haiku speaks of some oldie nos sonnotone tubes that are different from the standard ones sold through alo. These are the kind of old milspec tubes I would hope to eventually be able to find for the reasons you stated regarding manufacturing specs. Good luck with the Ray 6021. Hope its all the sound with half the heat/power consumption.