The tube amp won't be hurt if off. Tubes cannot be hurt because it has plates and need electrons to move via heat. Not sure what would happen with the MAC because of the back EMF through the transformers. . In any case like others has said it is very risky and a bad idea.
Two amps into one pair of speakers
This is a newb question, but my friend has two integrated amps hooked up to his speakers, one McIntosh and a Prima Luna. One is connected with banana plugs and the other with spades. He said this will cause no problems as long as they are not both sending signal at the same time. Is this true. It just seems a little strange to me.
TaterMike