The AXA25 does not include a headphone output, and there is no direct option for connecting headphones to the unit.
One potential workaround here is to use a headphone amplifier connected to the Rec-Out on the rear of the amplifier. It is important to note that this headphone amplifier will need its own volume control as the Rec-Out outputs a high level signal which could damage your hearing or headphones without attenuation. Due to this we wouldn't usually recommend this option, however this is a functional solution.