Hi,
I have a strange issue with one of my DN-X 1100. Since some days the preamp for the the headphones sounds overcooked on each position of the poty. The mixer was not moves, stand on the same place. Only thing which I made was to turn it on/off. I tried it with different headphones but sadly with the same result. 
Has/had someone maybe a simular issue with denon mixers or maybe is someone here who can give me tip how can I adjust it?
Thanks in advance.
This doesnt sound usual, or common. Does tapping the front panel around the headphone socket make any difference to the sound? If so, it could suggest that the mixer may have a faulty headphone socket or connector, rather than Pre-amp.
Aside from the usual headphone controls on the mixer itself, and of course, not running the incoming signals “into the red”, there are few other alternatives. The next step would be to get your mixer to an authorised Denon DJ service centre.