I hadn't used my amp for awhile, so I plugged it in and was playing, and it was working great. I was messing with the drive button and was generally adjusting everything to relearn what it would do. At some point after using the headphone jack etc. etc... It now will not respond to plugging my guitar in. Here is the weird part it sounds like it has a mic plugged in to it. I can tap on the front panel and it sounds like when you tap on a mic. It doesn't pop or anything when you plug in the cable like it should. Any ideas?