I bought a Zakk Wylde overdrive pedal to add to the overdrive I already have in my Blackstar HT-60. The pedal gives me a horrible humming when I turn it on, I do not have either gain turned up over halfway, on the amp or the pedal. Without the pedal, if I give the amp full gain, there is a very very faint hum, it just get's pretty nasty when I turn the pedal on. Is that just the nature of adding more overdrive to the overdrive that is already there? I already took the back cover off my guitar, checked resistance and continuity of all the grounds and everything is .1 ohm, from any ground to another including the tail piece. It also does not go away when I touch the strings. If it is what it is, fine, I can get used to it and just control it with the volume knob on the guitar, but if something can be done about it, than I would like to fix it. Thanks for any advice.