Anyone experience a ringing with their DT 50? If I hit a sharp staccato chord, my amp is left ringing. here is no reverb on the amp or on my hd500. I once the ringing (almost feedback) starts, it does not go away even when I turn my guitar volume down. I can even turn down the master volume on the amp and the ringing/feedback volume reduces in sync with the turning of the volume control. when I turn the volume back up, the ringing/feedback grows louder. I change patches the ringing stops until I hit a sharp staccato chord and it starts all over again.