Quote Originally Posted by struth View Post
some sort of impedence mismatch maybe causing it
No. It can only be a faulty power amp if it doesn't do this with other power amps. There is no fault which could cause this in a typical power amp and so I guess it must be to do with this overload protector or some such. This will be specific to Cambridge Audio so that's the end of the line as far as fault diagnosis goes I'm afraid.