New Ground Loop - What Could Have Caused?

Check your cables and connections. Unhook your video coax cable connected to your system and see what happens.

If the above doesn't help, check to see if there were any storms in your are that could have caused damage to your equipment (if left plugged in) or something else from a nearby lightning strike. Also ask neighbors if they had anything strange happen (electrical) while gone. This would be a possibility if disconnecting the cable doesn't eliminate the hum.

It was the Verizon FIOS box. Once I disconnected IC's running from FIOS box to pre, problem solved. No music statons through stereo, though.

Not sure what happened. I had no problems for years. There may have been storms and the units were plugged in while I was away.

Gremlins in the wires!

Thanks, folks.

Neal

It was the Verizon FIOS box. Once I disconnected IC's running from FIOS box to pre, problem solved. No music stations through stereo, though.

Not sure what happened. I had no problems for years. There may have been storms and the units were plugged in while I was away.

Gremlins in the wires!

Thanks, folks.

Neal

Nglazer,

Somewhere outside your house there should be a grounding block for the Verizon FIOS incoming cable before it enters your house.

The ground wire that connects to the ground block is supposed to connect to the main grounding electrode system of your main electrical service.... You might want to check and make sure that is how it was done.

The ground block should not be connected to a dedicated ground rod that does not tie back the main grounding electrode system. Not only can a dedicated ground rod cause ground loop hum problems especially when the soil is dry but it also can add an alternative path for lightning.
Bad news for your audio equipment and TV.

If the grounding block is properly connected to the main grounding electrode system and was working just fine until you came back from vacation then the ground wire connection at the grounding block could be loose or corroded causing resistance at the connection. A difference of potential, voltage, then may exist from the Verizon FIOS cable and the equipment ground of the electrical system of your house.

If there is a difference of potential and a closed current path is provided then you will have a ground loop and the dreaded hum.

Best thing to do is buy a ground isolator for the Verizon FIOS incoming cable line.....