“Why is my new interface so noisy?”
“Why do I hear noise from my speakers, even with the gain knobs set to minimum?”
“How can I get rid of that hum, without using a DI?”
“I just got a new powerful workstation and now the firewire port in my audio interface is fried”
“Why my cat died when was she catwalking around my mixer?”
“Why do I hear strong hum when inserting jacks in my mixer?”
The problem is short and simple, the story is long and funny 😛 Ground loop. Use one power outlet for ALL your electronic devices in the home studio. Yes. And do not allow any other ground connection to interfere. For example, if you, for a weird reason, are connecting your TV cable to your PC (I do, is so fun to hear TV on studio monitors :P) , you have allowed a second ground level to interfere. This is bad and can create havoc. You should connect the TV cable ground to your electrical ground (power outlet) BEFORE your TV cable enters to the system. Ok, take your soldering iron and solve the problem. It will take 10 minutes.