Not sure if we are on the same page. I have no hum with headphones, I just have hum when I am using my floorstanders as headphones :D, I have no hum too when I use the floorstanders as speakers. :D It's also not exactly a hum, more like white noise that has low frequency element, that varies with volume setting, so it has to occur before the input stage. I am guessing it is RFI related, and I haven't covered it up. My Beta 22 is similar (but better, though it is cased), although it used to be silent, I supposed I made some changes that I am not aware of.
I don't recall paying a lot for the clear tops, but I got them used, I paid less than a pair of new production tubes for 3 of them. They may be a bit on the bright side, but I prefer to call it sparkly. :D That only happens after a week, after I fed music at max volume for a couple of days. And only a few days ago I hear some really low bass coming out of this thing. I think my coupling capacitors aren't settled yet.
I also ordered some Sylvania 12BH7 and Philips JAN 6922, let's see.