Hey everyone. I have a Peavey express 112 (sheffield) 65watt transtube amp. Now, everything is working perfectly, there isnt anything wrong with it, but when I turn the amp off, there is a loud POP! What causes this? How can I make it stop popping? I've tried turning down the volume, all the knobs. It doesn't do it if I turn it off while my guitar is still producing some noise. Like for instance if I turn the amp off just after hitting all the strings. Anyone have any ideas? Thanks.