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.
As long as the plate/screen dissipation are below the maximum rating, high plate voltage isn't really a problem (see discussion above). Most commercial amps aim for the highest output power, so Class aB is the norm.
