I got an MXR Bass Octave Delux pedal for Xmas. I love playing with this pedal! However, I am noticing that there is often (inconsistently) a low noise that prominently sits in the background. Almost like a low static sound - definitely not part of tracking what I am playing. Is there something I am missing about the set up for this? (Running dry straight up, growl at about 10:00 and girth straight up, the internal mid-range adjustment is set as it was coming out of the box.) I thought it might be part of the "growl" setting. It is definitely worse if I run it with girth turned all the way down and growl at about 12:00. But evening when I run it with girth at 12:00 and growl all the way down - its still there - obviuosly! Did I get a dud and should contact MXR about a replacement or is there some set up tweak I am overlooking?