I have a sony str-da2400es and kef kht 2005.2.when the amp volume is set below 30db the psw2010 sub cuts out and goes into standby after about 30 minutes,i normally run the sub in auto power mode.if i switch to manual power mode it works fine.Have i set something up wrong or have i got a fault in the amp or sub.the sony amp is new this never happened with my previous denon amp.Has anybody got any suggestions.