Hey Peeps

I got a problem with my radio, I hope someone can help me with it. I brought a clarion detachable face radio and 12 disc CD about two years ago . I also brought a punch amp. and two JL 12's around the sametime. I recently noticed that when I drive for two hours or more with the stereo loud, eventually the music starts to break up. I have to turn the radio down and it will play okay again. It seems like it happens with the internal/ stock speakers only, which are not hooked up to the amp. This never use to happen before. I'm trying to pin point the problem. Any help would be appreciated. Thanks

Dave