You could also consider a Jensen transformer between the preamp and amp ( I don't like to add transformers because they distort but it is an option that may work for you - Jensen are high end transformers). I hope you are using only XLR connectors? If you use RCA then hum is not uncommon. A trick with RCA is to use an unshielded twisted pair - as ground loops are usually picked up on a shield.
Ground Loop Hum
Hello, I am looking for help eliminating the hum I get in my subwoofer. I have a Rel B1 and am using the high level inputs. The Amp I am connecting it to is a BAT VK-600. Based on the documetation this should be treated as dual mono blocks so I have the two hot wire connected and the ground going to my pre-amp ground. I have tried different grounds including the one on the power conditioner. I have tried all the normal tricks of moving where the cable runs, unpluging all other componets, etc.
Any thoughts would be appreciated.
Any thoughts would be appreciated.