REL Q150E Humming


Standard Member
Hi all, I've had a REL Q150 for a while now. It's hooked up to my 3 Arcam Alpha 10s (DAVE), alongside a pair of Monitor Audio PMC 703 speakers, a KEF 100 centre speaker and a pair of Mission rears. It all works very nicely.

My issue is when the Arcam system is put into standby or turned off the REL Q150 starts to make a loud humming noise. When the Arcam system is on it is quiet.

I've checked the earths but all seems fine. Does anyone have any ideas or tips for sorting out the humming apart from unplugging the REL everytime I turn the system off?

My logitech z5500 sub does the humming sound to when it is in standby I heard it might be something to do with not having clean power, so i'm looking into getting a high end ac cable and an AC Line Conditioner to clean up the power, you could try plugging your system into a surge protector to see if that makes a difference...

check this link of an ac power conditioner... home.htm

also check this post..


Distinguished Member
make sure you are using a decently shielded LFE cable to hook up the could be that when the system is off the sub is drawing signal from something else....too thin/badly shielded a cable is basically an

if not then its probably your mains supply, but to be honest it should be humming all the time with that....

Deleted member 30535

Try this little "trick" first:

Use an interconnect which has only its shiled grounded at one end, and free at the other.

The hum sounds like ground loop problem where items in your AV chain are at slighty different "earth" potentials and a current is induced on any path between them...... interconnect shielding is one of them.

Then of course what I did was just disconnect the earth. Same difference as far as breaking the earth loop circuit. Thats' stops the feedback loop too, but I have residual current breakers in my house so that is not an issue for me.


Established Member
I have the same problem with a BK subamp which is hooked up with the neutrik cable the same way Rel does
when I put the system on or off the huming can be heard, system on no huming
so in my case there is no interconnect used
the neutrik cable is connected to a pioneer vsx-d1010 receiver


Standard Member
After some more investigation I find that if I disconnect the RCA phono lead, leaving just the Nutrik cable and the power cable connected it still hums.

If I disconnect the Nutrik cable from the AMP leaving the bare end free - it still hums.

However, if I then disconnect the Nutrik cable from the REL it stops humming!

If I connect just the RCA phono lead without the Nutrik cable - no humming can be heard.

I assume that the Nutrik cable is causing this!


Standard Member
Got this reply back from REL today:

Dear Gareth,

Thank you for the additional information.

Your problem appears to be the result of the design of your amplifier.

The REL input circuitry ground uses the common of your amplifier for the signal ground.
What happen is when the amplifier is switched off, put in to standby or unplugged, this common connection does not exist anymore, resulting in an 'open line' to the REL which causes the REL to hum.

An example of this is something that you have already tried.

'Connecting the hi-level cable via the Neutrik connector to the REL and leaving the other end (ie. the red, yellow and black wires) disconnected, the REL hums loudly'.

Basically, this is what is going on inside your amplifier when turned off, in standby or unplugged from the wall.

Unfortunately, there is not much that can be done except to switch the REL unit off along with the amp and shielded cable won't help in this scenario because the common from the amp has still been cut out. Please remember that if this is the case, neither the amp or the REL unit is faulty, it is purely the result of the design of the amp.

Member 14718

Established Member

I think that a screened cable may work. When an amplifier is switched on it has a very low impedance, this prevent any hum pick up in the lead. When you switch the amplifier off the impedance goes high (maybe a relay clicks out) this then causes the hum to be picked up by the high level lead. It's not a fault with the amp or the REL it's just how things go.



Standard Member
Ok well, I've bought myself some screened cable and a Neutrik speakon connector. I'll try that tonight.

I've also had another reply from REL saying that I could try connecting the black wire from the hi-level input to a earth on the amp (i.e. the phono stage earthing point). They did however point out that this was AT MY OWN RISK !

I may try this afterwards if the screened cable doesn't work.

I'll post my results up later.

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