My Spider II 112 (75watt) amp is issuing a disturbing crackling noise that sounds like a short in its wiring. It sounds like "Insane" but crackles very badly, just like a bad connection. I have checked my guitars wiring, ground, pick-ups, jack, and bought a new cable. As long as I select Metal or one of those six settings without touching either Drive, Bass, or Mid, it works fine. Treble I can adjust without it effecting it. One little touch to any of those three and it goes straight to crackling....it will still play any of the six Amp Model settings, but with that crackling noise permeating the sound faintly....but when I stop and mute the strings, it's loud and clear. Somebody please tell me they know what this is and how I can make it go away!