I love the 46 DHT. To the extent that I went on the crazy idea to implement it in filament bias. It was my winter heating indeed. Stupid idea, but sounded brilliant.
I had several questions about the 46 lately. As I’m rebuilding my 300B amp, I’d love to play with the 46 again. Here is how I’d implement it today:
The gain of the stage is about 40. The 46 has a mu of 5 in triode mode. Instead of burning loads of heat in the filament bias arrangement, I use a degenerative cathode resistor (unbypassed). The input set up transformer is the brilliant LL7903 wired in 1:8. I have a PCB made for this which it’s very handy. A zobel arrangement (C1+R2) helps taming down the frequency response at HF. Running the valve at 30-33mA is ideal. 200V at the anode is ok and the HT may be adjusted depending on the swing you need here. The stage has all the bearings to drive whatever output stage. I will add a source follower prior to the 300B as I run the 300B in fixed bias mode.
Hope this helps
Ale