I've never been averse to using props during presentations. At this point I whipped out an actual 6SN7 I'd bought a couple of days before at Electronics Plus. Unfortunately, neither nanotechnology nor multimedia have as yet advanced to the point where I can make a vacuum tube pop out of the page as you read this. But, you can turn to page [Ref] and see a schematic of the circuit I'm talking about. All is one. Or something.