2e24 DHT

IMG_0369 SMALL 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:

2e24 triode SMALL

Ra is on the range of directly heated pentodes wired in triode of similar size. Here is the triode model matching these curves:
2e24 triode SPICE modelNow let’s see how this little fellow will perform with a Zaa=6k5 load:
2e24 triode 6k5 loadline

Not that great, probably will be better in Schade feedback:

2e24 schade SMALL

2e24 schade triode modelApplying only 10% of feedback reduces the Ra to about 1k3 and the triode SPICE model still matches quite well the curves. So how will perform then with the same load?

2e24 schade 6k5 loadlineWe 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…

One Reply to “2e24 DHT”

  1. Hello Ale,

    Nice work there.
    Can you tel me what version of paint_kit.jar you use for tracing tube parameters?
    Is public one or…

    Thx in advance!

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