Your amp is trying to pull to much current and the fuse (probably 15A) can't handle it. Try the next size up (20A). That should do the trick. If you have to go higher than that, then your amp may be defective.
Sounds like you either have a fried transistor or any other component. In my experience tranisistors alway seem to malfunction first. I wouldn't recommend steppnig up the fuse amperage unless you want to smoke more components. Which could also lead to a fire in your vehicle, etc etc.
If it is a new amp take it back, if it is old either take it to get it worked on or price out a new one.