Al, thanks so much. I think that using power resistors, as you suggested, is the easy proof of your theory.
The panels in those MLs are probably highly capacitive so that may support your supposition as well.
The Stereophile review of the M-180 (they did not test the Zeus), shows good behavior in triode mode but a single cycle of undamped ultrasonic ringing in UL. They did not test the amp with a capacitive load, and it is a different model so I am not sure that any inferences can be made from this.
The panels in those MLs are probably highly capacitive so that may support your supposition as well.
The Stereophile review of the M-180 (they did not test the Zeus), shows good behavior in triode mode but a single cycle of undamped ultrasonic ringing in UL. They did not test the amp with a capacitive load, and it is a different model so I am not sure that any inferences can be made from this.