REL r505 Hum

Hi everybody,

New here, already read a few topics about the REL hum issues but didn’t see my specific case.
I have 2 REL r505’s which I love. They are fantastic.
They are connected to a Vincent hybrid tube amp with REL speakon high level cables.
Unfortunately there is a hum when I turn OFF my amp. When the amp is turned on, there is no hum.
I tried disconnecting the BLACK wire of the high level cable, and grounding it to the amp, as told by REL. I also tried just disconnecting it and taping it. Also connecting a RCA cable from amp to 1/LFE doesn’t do the trick.
I even shielded the high level cables with a PVC tube, behind the component rack where other cables maybe interfere with electromagnetic radiation.
I’m out of clues.

Greetings from the Netherlands,


Welcome Bram,

  • Is the REL quiet when nothing is connected (onlys the mains)?

  • Are the REL’s plugged in in the same powerblock as the amp?

PVC tube gives isolation but no shield.


  • Is the REL quiet when nothing is connected (onlys the mains)? Yes

  • Are the REL’s plugged in in the same powerblock as the amp? No



It could be a ground loop.
I dont know what is connected to the Vincent.
But you could try to disconnect all inuts of the amp en reconnect it one by one (amp off).
If everything (except speakers and mains) is disconnected and it still hums then you could to try connect the amp and sub’s to one connecter block.

Please turn down the volume of the SUB during disconnecting to avoid damage

Another question: If the Vincent is switched off the Sub’'s should go in standby or?

The Vincent is a main and pre amp.
The main is connected to the pre amp, also a DAC is connected to the pre amp.
The DAC is connected to a media player.
When the main is disconnected, the hum even gets louder “in the middle” of both subs.(Amp is turned off)
When I listen closely to the sub, the original hum is still there.

I tend to think the SUB speaker cables pick up interference.

Also connected subs and amp in same connector block earlier, without result.
I now have the subs in both ends of the room so connecting them in same block is not possible anymore.

When the amp is turned off the subs remain in standby mode.
But because of the hum I turn them off (on/off @ back of sub)

I have the hum when the amp is turned off. The people at REL can give you instructions on how to disassemble the sub and check to see if the subwoofer amp is properly grounded.
I simply turn off the main power switch on the sub when not in use.

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Hi Matthew,

I also forwarded this topic to REL so I’m curious what their answer will be.
Untill now I also turn off the subs but this shouldn’t be necessary. They should remain on and on standby mode.

could test ground-loop theory by removing the ground pin (but not sure if you have “cheater plugs” in the netherlands!)

I did this with my t/5i’s and it got rid of the hum.

i have the same issue as you, with my ragnarok 2, if its off the rel t9i hums, was in contact with rel and thay said that,its not so much you can do.

I also had same issue with T5i’s. I just powered them off when not in use.