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.
Yes that's a bit over the top, but I like the use of feedback to the screen instead of connecting the 4P1L in triode. Avoids most of the 4P1L current passing through the OT. I will try that in my ECL85 PP STC that I have breadboarded.