About a month ago I found a little pack at an electronics supply store (think Radio Shak type) that was labelled "study pack: vacuum tube technology". I grabbed it right away. It comes with a rather weird PCB, some resistors, capacitors, a coil, two LEDs and - interestingly - an NF amlifier chip. But the star of the collection is the included vacuum tube and a booklet that explains some basic appliances of it. One of which is a pre-amp that feeds into the NF amplifier chip... not really what I was hoping :) But the more interesting one is the headphone amplifier that I built here: two resistors, two capacitors, some wires and done. Of course it needs supply voltage (the battery pack is used to heat up the tube, the 9V block is used to operate the rest)
I've been listening to this weeks FPS broadcast for over two hours on this gizmo and it still runs. No adjustments, crystal clear audio. Neat.