Trust me, they hiss. If the EQ is set to anything higher than flat ..... you get hiss. Granted, it's not horrible, but maybe your situations and/or hearing loss mask it to a degree.
If you use the Noice gate - it becomes very clear just how much hiss the unit generates. It's not the mic input alone ... it's the general amp.

The Tyros may not have the same noise ratio. I'm just talking psr here.