This can be caused by tons of factors. Check the LED indicator on the amp to see if it is still powered up. Also, if it has one to show it is going into protection, check that as well. Here's a few ideas to help you figure it out. 1. Check the input sensitivity on the amp (gain) if it is turned up to capacity, TURN IT DOWN! Afterwards, turn the volume up a little more, until it shuts off again. Keep doing this until you get the radio to a reasonably loud volume, and it doesn't cut out. 2. Check the wiring configuration of your speakers. I'm assuming you are talking about a subwoofer amp. Depending on the impedence of the subs, you may have them wired too low for the amp to remain stable at louder volumes. Comment on this question to tell us what kind of subs they are, and how many ohms they are. 3. Check the connections (battery, ground, remote, outputs, and RCA's). The connections could be loose and disconnecting, or not have enough wire strands to support a heavy power draw. 4. You may be running too much current through your power wire. What gauge is the power wire? What it the RMS output of the amp? 5. It may be due to overheating. When the amp shuts off, is it very hot? A fan, better positioning for ventillation, or again turning the gains down so it runs cooler may help. There's a bunch more you can to to fix it, but more info will be needed. I hope this helps.

here's a wild idea - don't turn it up full blast.