• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Conflicting 807 plate impedance

6vheater, it is becoming apparent that you haven't even read the references you are highlighting as works that Williamson copied his circuit from.

Did you read the A503 article and inspect the circuit? Same for Cocking's various articles in WW? Cocking appears to have started contributing WW articles in 1929, and started the 'Quality Amplifier' series of articles from 1934, so I think you are misinterpreting whatever reference you are quoting, and just picking up a 'vibe' and waxing lyrical on that. Did you realise the A515 was Langford-Smith and Aston's effort to copy the just published Williamson circuit as best they could with their house brand valves, and that assessment led them to do a manufacturer life assessment of the 807 at the Williamson amp's higher screen voltage level?

Perhaps you keep getting reflux whenever the 807's use in amps comes up in a thread, because of your bad luck with one sample of 20 valves out of the 'mega zillions' that have been used.