• 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.

Philips output transformer?

> these DCR's have no relation to the circuit impedances.

True. But DCR on wideband audio transformers is very often 10% (20% to 2%) of the nominal Audio impedance. So not an Answer, but a Clue.