I recently was hearing some ground HUM with my new setup rig, after isolating the source & investigating some remedies to fix the problem someone recommended this little inexpensive beauty from Pyle Audio to eliminate the annoying sound.
And let me tell you I am so glad they did and as described the HUM is gone and I am a happy camper once more.

https://www.amazon.com/PYLE-PRO-PHE400-Eliminator-2-Channel-Outputs/dp/B00BARTW42