if there is a hum there is a ground loop. the transformers suggested above will fix it but it should be able to be fixed with a cable. if you can solder you could build a cable for $10 that would test this. I would also check if the A/C plugs for both the classe and the griffon are plugged in the same direction.
The other option is that there is a ground differential between something connected to the classe and the griffon. unplug all inputs and outputs from the classe including those to the tv and connect them to the griffon. does it still buzz? Add them back in one at a time to see what causes the buzz.
The other option is that there is a ground differential between something connected to the classe and the griffon. unplug all inputs and outputs from the classe including those to the tv and connect them to the griffon. does it still buzz? Add them back in one at a time to see what causes the buzz.