2. speakers
  3. 188003-46

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
Post removed 
bolong
384 posts
 

Is your system on a dedicated AC line?

last_lemming OP
631 posts
 

It is dedicated  

 

i’ve also noticed that if I move the speaker cable around disconnected from the amp, it changes the hum, almost like it’s acting like an antenna for it

last_lemming OP
631 posts
 

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!

mofojo
2,172 posts
 

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

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