There is a ground loop coming through the sub (Current Audio FLSUB10). At first we thought it was a defective amp on the sub and Current Audio sent us a new amp. Installed the amp and issue still is present.
The sub is connected to a Denon AVR-X2400 approximately 70' away.
After more troubleshooting the ground loop is being introduced through the HDMI cable connected between the cable box and Denon amp. Tried multiple different HDMI cables (6' HDMI cables, a couple no name and Crestron cables), and a couple different cable boxes and still obtaining the same result (sorry didn't get the model of cable box but they are Cisco 4k PVR and non-PVR boxes).
Also tried different inputs on the amp and still the same result. As soon as the HDMI cable is disconnected from either the cable box or Denon amp the loop disappears.
I have tried grounding the incoming cable feed (provider didn't ground it), ground the chassis of the cable box, and ground the chassis of the Denon and still did not correct the problem. The Denon and cable box are plugged into a different circuit than the sub.
Only solution is to temporarily remove the ground on the subwoofer so the home owner doesn't have to listen to a hum from the subwoofer.
Looking for a proper solution that is cost effective as we will be the ones paying for it.
We have the same installation in another house using the same equipment and are not getting a ground loop (houses are a block apart).
