Troubleshooting hums and buzzes are difficult. There are many reasons why there are buzzes and hums in audio equipment, and one reason is ground loops. The Hum Eliminator could be the solution to your issue.
When you plug in a piece of gear into your system, and you start to hear a hum/buzz caused by a ground loop then putting a Hum Eliminator in the signal should fix the issue.
WHAT IS A GROUND LOOP?
A ground loop is when your ground and shielding create a circuit. For example, you can have a radio receiver (do people still use these?) connected to a powered speaker. The receiver and speaker use three prong power. Do you see the ground loop? The ground is now linked from the receiver to the powered speaker through the audio line shielding. Each piece of gear plugged into the wall outlet has their grounds tied together. See the ground loop now?
AC power in the power cord can induce an AC current in the ground loop. The AC Current in the ground loop then induces unwanted electrical current into the audio line, which is amplified as noise. Notice I used the word "induce" a lot because this is known as induction.
If you are the contractor and installing a patch bay or a full studio of equipment, then you should look into "star ground" or "source termination." You can do this in a home studio as well but know what they mean before attempting. Even if you are doing these in your studio, it's still a good idea to have some Ebtech products. Just the other day, I brought out a groove box (drum machine), and I started having a crazy hum out of my speakers. I used a Hum Eliminator in the audio path, and all was good again! Fast and easy!