Ground loops mentioned again: can I ask for clarification as it's slightly off (SU-8) topic?
I usually hear of ground-loop issues from Americans and hardly at all from other nations. Is this an issue more prevalent in USA than elsewhere because of the way electricity is supplied there? Rightly or wrongly, my reading all over the www has led me to the conclusion that power supply in USA is more 'dirty' (not properly grounded) than elsewhere. Maybe because it is such a very large country, power infrastructure is difficult/complicated? In this case, sure it would be similar in Russia or China? I don't get it?
This is definitely massively off-topic (so we should probably try to keep this short if anything), and I'm by no means an expert here, but I can attempt to tackle this a little bit. Anyone else can feel free and step in here if desired for correction and/or clarification.
"A ground loop occurs when there is more than one ground connection path between two pieces of equipment."
So you can create a ground loop fairly easily. And the thing is, once you start having multiple audio components with separate power supplies, factor in a PC (if you're using one), and then powerstrips and separate outlets, and boom you have a ground loop fairly easily if you're not paying attention.
In my case, I'm not in the USA. I'm in Switzerland, which typically is known to have a pretty solid grid/building regulations. And I never had these things when I was living in New York. I believe it ultimately comes down to the grounding design of the building/house itself. Namely, if it has more than one path to ground (let's say the circuit that leads to a particular outlet has one path, and another circuit, and outlet, has another path), then if you had two components connected to each other, and both of these components connected to these two different outlets, you would create a ground loop.
The effect of ground loops can vary in degree, but usually there's a "hum" that you can very audibly hear in some of your equipment. And you can usually tell it's a ground loop if you are listening to the equipment and you put your hand on one of the pieces of equipment (that's metal), and it changes the tone in some way.