• 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.

current drive

The simplest way to get current drive with valves is to use a pentode output, perhaps with cathode degeneration (i.e. local feedback). It will probably sound awful, unless used with specially-designed speakers.

If you want to add extra more global feedback, take the feedback signal from the degenerated output cathode. This means it samples a proxy for the output current and increases output impedance.