Is Belles 350A amp fully balanced in mono?

Can anybody tell if the Belles 350A is fully balanced when used in mono. I have a friend who has a pair of 350A and he wanted to try them on his Vandersteen 5A which he has the balanced crossover only. If they are fully balanced meaning both legs of the balanced circuit is the same, what is the input impedance?

I looked everywhere and it doesn't say. There's XLR jacks but that doesn't mean anything. Anybody know?

Thanks....