REL Hum. Stumped


I’m getting a hum from both my REL subs. The strange thing is the subs don’t even need to be connected to the Luxman integrated to hum. All I have to do to get them to hum is plug in the Speakon connector.  If I disconnect the Speakon at the sub the hum stops. 
 

Connecting the high level wires at the amp doesn’t stop the hum;

nor does connecting the black wire to the amps grounding lug.

nor does running an RCA from an input on amp to the unused LFE input on sub

nor does using HumX to lift the ground

nor does changing outlets

nor does using the same outlet as the amp

nor does using a isolation transformer 

 

Btw the amp doesn’t even have to plugged in and I get the hum!

Im lost, any thoughts on what I should try next. 

last_lemming

Ok solved it!

 

The clue was the fact when I moved the stock cable around it would pick up hum next to certain devices so I assumed EMI.  So I made shielded cable  

I bought some 4 strand shielded copper cable from Home Depot. This cable has 4 coated copper wires and a fifth un-coated with a foil sheath.

The un-coated wire that runs exposed along the foil sheath in continuous contact with it.  I soldered the uncoated wire to the black coated wire thereby creating a grounded shielded wire.  I abandoned the white wire, and used the red and green wire as the hot wires. 
 

zero hum!

Nice good job 👍. I was gonna suggest a cheater plug to float the ground. 

Had a similar issue with my S/812.  
 

For some reason on AC in my duplex outlet caused a hum.  The other did not.  
REL suggested running an RCA (assuming you are using high and not low connection?) to my integrated.  That helped as well.  
 

Now however I power the sub through my Transparent PowerIsolator (conditioner) and that has entirely solved the issue.  Frustrating.  Good luck!

As a side note do not connect the black Speakon wire to the speaker terminal if it is a balanced amp or has XLR inputs. If you must use it connect it to chassis ground ( or a chassis screw). That is cool you figured it out. I use upgraded power cables on my subs. I know some manufacturers say you have to use their cable. I think it’s a guage min. 

Please don't use a cheater plug for extended use. The work as a trouble shooting tool but are dangerous if there is a short. They are designed to provide a ground on an old two wire house not lift the ground of a three wire system.