By 'noisy' do you mean distorted or just loud? If the former, there may be a problem with settings. If the latter, there's not necessarily any problem; the X3 is a powerful beast. Protect your ears by turning the Master volume down before you plug in the headphones and then turn it up to the desired volume.
The manual actually anticipates this. Here's the snip....
Phones – plug your headphones in here to avoid noise complaints from the
neighbors (or the rest of your family). The volume is set by the Master Volume knob.
Any time you use headphones, it important to be sure they’re not set for ridiculous volume
before your slap them on your ears. Try a Master Volume knob setting of about 10 o’clock
to start, then turn up from there if you need more volume.
Have you tried your headphones in something else to make sure there isn't a problem with the headphones?
What happens if you switch on the noise gate in the patch you are using?