I dug an old 15 watt Marshall MG15 out of the basement for recording and realized why it was there in the first place. When I turn it on there is a high pitched tone that doesn't go away. It seems that all of the amp's regular gain settings occur between 0 and 1 on the knob and anything after that just gives horrible horrible feedback. I have no idea how or why this is happening but I've opened it up and don't SEE anything wrong with it. Then again I'm no electrician, just a musician.