Not on the Tyros, Toril.
All headphone outputs nowadays are limited to a certain Db because if it's too loud, it could damage your hearing.
But if you're using the headphone socket to drive a monitor system, (such as a Yamaha Stagepass) there's plenty of power coming out of the headphone socket anyway.
Short answer is if the headphone socket is going into a mixing desk, a 250,000-watt concert PA system even a small one, then the preamplifier will boost the sound (theoretically) to blow the **** roof off whatever gig you're playing.
The output on the headphone socket is pretty strong, Toril, but I'm just a muso, not a roadie! ;-)
Norm.