A tube is a tube is a tube. If one side emits electrons, another collects them, and a further terminal can block them, you just know that someone’s going to use it as an amplifier. And so when [Asa] had a bunch of odd Russian Numitron tubes on hand, an amplifier was pretty much a foregone conclusion.
A Numitron is a “low-voltage Nixie”, or more correctly a single-digit VFD in a Nixiesque form factor. So you could quibble that there’s nothing new here. But if you dig into the PDF writeup, you’ll find that the tubes have been very nicely characterised, situating this project halfway between dirty hack and quality lab work.
It’s been a while since we’ve run a VFD-based amplifier project, but it’s by no means the first time. Indeed, we seem to run one every couple years. For instance, here is a writeup from 2010, and the next in 2013. Extrapolating forward, you’re going to have to wait until 2019 before you see this topic again.