If you've ever had that annoying problem of your GK MB500 losing that brilliant sound that becomes scratchy, hissy, dull, crashy, etc. then this might be the fix for you. Disclaimer: My best advice to you is NOT to try this. Get it taken care of the right way by the manufacturer or a certified / licensed technician. However... If this works for you... GOOD. If it doesn't, go and BUY ANOTHER GK MB500. Gallien Krueger products or nothing!!! Watch the vid... before and after.