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.
A little more complicated here than clamping 2*vbias reverse blockage.
The forward conducting cathode voltage is a moving target that climbs
with the output level.
Do we risk a situation where bias runs away in the positive direction?
