Just bought a Cambridge Audio 640A. When i play music with the volume about half way up for about ten minutes it gets hot and shuts itself off. Is this a problem with the design or did i get a lemon. I am drving Jamo E650's.They are 6 ohms and about 90 sensitivity.(not hard to drive).Can any cambridge owners comment.Do your amps get hot also. Half way up is not that loud so i'm pretty pi*#ed off