I own a schecter demon 6. I have been practicing a lot using the metal mode on my Spider line 6 amp. Today when i tried to get a clean tone, and i am unable to get it. Have tried multiple amps,no luck. Used a different guitar on the same amp settings and that is giving a clean tone. There seems to be an added distortion/noise to the sound. I am assuming issues with the guitar pickup. If anyone has faced this before, please advice.
If your demon 6 has active pickups (not all do), it may be a weak battery.

If the pickups are passive, perhaps if the guitar was previously owned by somebody else, the wiring or pickups have been changed. There are several after-market "distortion kits" that can be added inside guitars.