I have a Peavy TKO 115, it's about 7 years old. Recently, I've noticed that it's producing a distorted sound, as if I was using an actual distortion pedal, or had the overdrive cranked up all the way. My first conclusion was that there might be a crack or a tear in the speaker cone, but I removed the speaker and examined it closely, and I see no sign of damage. When I put the speaker back in and turned on the amp again, the noise was gone. Since then, I've had a couple more instances of the distorted sound returning, and I just removed the speaker, put it back in, and the distortion stopped. Has anybody else ever encountered a problem like this? Just for info's sake, the amp was used regularly for the first few years I owned it, then sat in a closet unused for about 2 years. I started using it again about a year ago. I have a Vigier Excess II bass and a Fender Jazz Bass MIM, and when the amp's making the noise, it does it with both basses. Thanks for your help!