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.
This is how to measure the damping factor of your amplifier in LTspice.
I also changed the output-transformer model (reversed the output inductors) so OUT now connects to S8.
