Thanks Marc - actually I am using Monster Cable Z1's for the M80Ti's and these have plugs with no exposed wires as I'm sure you're aware. I've looked at the back of the AVR520 and speakers to make sure everything is OK and not reversed and it's fine. Also, I've now tried connecting this to a TrippLite UPS computer battery backup and the same problems occur. Turn it up past -16 give or take and it will go into standby after a few seconds up to a few minutes. Should I be calling Harmon / Kardon now?

Thanks,

Doug