Dear Sirs. Can anybody please tell me why, after for example, 15 minutes does my amp cut out? The mute indicator will pulsate rather than just constantly illuminate if the mute is operated. I suspect it may be a warning device, perhaps signifying overheating, however the amp is very well ventilated, in fact it sits on it's own. Otherwise it appears to be working perfectly. Hope someone can help. Thanks in advance. Chris Dean