Well its not a problem from the mains external to the machine as Ive
isolated the machine and filtered the mains with a 6-Way Mains
Conditioner but I do now think that it is internal mains hum as I have
done everything I can.

I did receive an email to say that a lot of home cinemas with dvd are
prone to making a hum noise when played at low volume

So guess Iam stuck with it, I now disconnect the woofer if Iam
watching or listening to anything that I want low volume on