Ground loop is something I'd describe as hum due to 50hz cycle.
If it is ground loop then read this for all the info you'll need to safely fix it. If your amp is fitted with a ground connect(virtually all are) do not remove the ground wire from your amp as its unsafe and illegal.
If your having trouble differentiating between hum and buzz there's one sure way you'll be able to identify. No doubt you've heard one of these in action(seeing one in action is another matter entirely) and if your noise sound like this then you have buzz: