Russian rod pentode circuits

[Kalee20]

Excellent Kalee.
The frequency response is really good.
What is the distortion levels?

Thanks! Though I don't know - distortion has not been measured.

I do have scope traces of the output, just below the clipping point, with both sinewave and square wave drive. The sinewave looks pretty good and sinuous, so distortion is at least low.

You can see residual HF noise from the HF AC filament heating, as mentioned before, some optimisation here would no doubt clean it up. But it's not a problem.