It is most definitely your power cable. You need to make sure that you use a 1 ga solid power cable and is heavy enough to hit a home run at Fenway Park if you can lift it. Make sure it is Oxygen free, solid copper, twisted in the same direction as the rotation of the earth, was manufactured under the same astrological sign as you were, meets your state carbon emissions limits, and most importantly "fits" in your hand so you are comfortable with it on stage.