It was suggested to me recently by Piotr to explore the 2e24 after looking at the 2e22. This small directly heated pentode have about 10-12W of anode dissipation depending how it’s wired. I suspected this DHT in triode mode will have a high anode resistance so as soon as I managed to get hold of a sample, I submitted it to the mercy of my curve tracer:
Not that great, probably will be better in Schade feedback:
We can see an improvement by applying Schade-like feedback. We can squeeze out about 1.5W @1.1% THD but paying the price of a higher H3 component in the mix. Interesting to see that the driving requirements are low (about 54Vpp).
A valve that could be driven by a simple MOSFET common-source stage and will make a very small and simple amplifying stage…