Mains hum

This is probably opening a horrible can of worms, but is there a cheap and easy way to reduce a low-level background hum from one’s speakers?

Thanks in advance.

Is the hum present with nothing (other than speakers) connected to the amp or does if start only when something is added?

There’s only one thing connected, so I will experiment with nothing connected tomorrow (listening to Youth & Gaudi right now). Thank you.

I’ve already worked out part of the problem. It was “clean the house day” today (I hoover, she dusts) and the volume knob got whacked in the process - when I put the aforementioned album on it was satisfyingly loud.

That will do it. Even so, there might be scope to reduce noise. You have a Sonos thing of some description yes?. If so, if it’s a two wire mains device, it might be trying to ground via the input board which Naim isn’t a fan of so that might be creating audible hum.

Yes, Sonos + Naim.

Oh aye :face_with_raised_eyebrow:

It’s very common practise and there’s nothing bad about doing it… unless you also have an amp where the company leaves the input board floating cos it (apparently) sounds better.

There’s your problem right there.
Aggressive hoovering can ruin the quantum balance of the cables. You have probably broken a nanoparticle lattice resulting in the electrons losing their alignment…

Stick to dusting.


My comment was more related to me only having 5% of a scooby what you’re talking about.



Does the hoover sound better with the hi-fi disconnected?

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Did you manage to cure the problem?

Rather than shit on another thread, having just read Paul’s thoughts here

I thought I’d pop this one back open.

Hum is still there. There is definite mileage in Ed’s theory

that the shitty Sonos box is mostly responsible.

Basic observations, volume at 12 o’ clock so music would be put-you-out-of-the-room loud, by “connected” I mean plugged in with RCA phonos

  1. With the Sonos box on, on the “stream” channel to which the Sonos box is connected, the hum is very loud
  2. With the Sonos box on, on any other (disconnected) channel the hum is even louder :thinking:
  3. With the Sonos box on, but disconnected, there is a small background hum (you have to put your ear close to a speaker). So it’s not that the wall wart is fucking up the mains in general or transmitting nasties through the air.
  4. With the Sonos box off, but still connected, the same result - a small background hum

I know fuck all about this, but the problem is clearly when the Sonos box is both on, and connected.

Any suggestions other than buying an ND5 XS 2, or a DAC that would effectively isolate Sonos from Naim, or a new amp (yes, yes, ho ,ho)?

Might this

(taking a lead from Paul’s suggestion of the DC blocker) make a difference? £129 is a bit of an extreme punt.

Thanks in advance.


How are you switching the Sonos box on and off ? Are you doing it using an On/Off control on the box, or are you doing it at the mains switch to the wall wart ?

Does the wall wart have the ‘Class 2’ square-in-a-square symbol on it, as here

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This way.

Yes - I’m currently googling what that means :laughing:

Simplistically, Class 2 devices have very high quality insulation between the mains supply wires that go into them (Live and Neutral) and any wires that come out of them i.e. the ones to your Sonos box, or any other metal parts on the outside of the supply. If devices meet this standard then the manufacturer doesn’t have to safety-earth them, so he can use a two-core mains lead. This can help a lot if he’s making a product which will be used worldwide, including in countries where the safety earthing at the supply socket might not be nearly as good as it is in the UK. Two-core mains wiring is also a bit cheaper.

Perfect insulation stops any current at all from flowing through it. Or, more exactly, any DC current. But the mains isn’t DC. It’s AC, and AC can ‘flow’, to an extent, through anything (even a vacuum). So the safety standards have to permit a small amount of AC leakage current to flow. And some manufacturers of (transformerless) wall warts use this permission to get away with some low level of connectivity between the mains wiring and the supply’s output wiring. Sometimes, if they do this, they leave the Class 2 symbol off the device. So if you’d said there was no symbol on yours then I would suspect that that could be the problem. But you have found the symbol. So now I can’t be sure.

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I understood most of that, so I think I deserve a nice G&T :+1:

Thank you.


OK, I actually googled this and as ever there’s a weird little Sonos/Naim/hum corner out there.

The consensus seems to be, as everyone is hinting here, two pin mains on the Sonos and odd grounding arrangements with Naim.

The “solution” is

The wire is on the outer ring of the RCA.

Plug into a spare socket on the Sonos (i.e. the rubbish / useless phono ins), and allow the Sonos to ground to the mains earth.

This all looks quite deathy to me.

Pretty much the same as an ESD plug (Which ca be had for next to nowt)

Sonos don’t use external wall wart, it is a mains cable directly into the unit.

Must be class II though as they are figure of 8 two pin power cables.