Sonos hum and smoke!

Hello All, I’ve seen some very interesting comments on other threads about sonos and humming noise. James_n I will try your suggestion of connecting a phono to earth plug when I get my amp back.
So, I have Sonos as the only source to a Nait 5i for many years now and while I initially tried quite hard to find a solution to the constant hum I get, I have learned just to keep the volume as low as I can and try to ignore it. But, twice now, during a thunder+lightning storm the amp has broken (electrical burning smell) and it has actually melted the dust covers on the cones of one of my speakers. After the first time we were careful to only switch on when we used the system and always switched it off during storms. But now last week we had a single strike of lightning during a rain shower and again the amp and speaker blew up. (And this time there are no more replacement speaker drivers) There was actually smoke coming out the speaker which is not something you expect to see!
Anyway, after reading some posts I am now linking the two issues together - hum + fragility - and guessing that the problem here is lack of grounding.

So after all that, my question is … can anyone please tell me if connecting a sonos input phono socket directly to mains plug earth will solve the grounding problem and prevent everything from blowing up again during the next storm?! I know from other posts that it will likely solve the humming issue but I really can’t handle it blowing up again.
Also, should the “grounding plug” be in the same power adaptor as the amp & sonos, or should they all be separate or does it make no difference? They are currently plugged into a tacima power filter thingy but this obviously didn’t prevent the power surge that I presume happened. Nothing else in the house was damaged either time by the way, only the amp+single speaker.

Thanks in advance for any help or suggestions,

The only way to remove risk of lightning damage during a storm is to have a large enough gap between the electronic item and any wiring connected to the mains, or to a telephone wire, or an aerial, or to metalwork in the house unless said metalwork is substantial and extremely well grounded or effectively forms a Faraday cage around the equipment. Whilst there are means of supressing high voltage spikes on wiring introduced by lightning perhaps well away from your home, that is only up to a point - and certainly won’t rotect against a direct strike on the wiring in the house, or above ground externally. Even switching off at mains switch on the wall offers little protection as the voltages involved with lighting has no trouble at all jumping the contact gap in a switch. It also has no difficulty jumping to an earth/ground wire and through that to the equipment as well as to earth. Earthing the phono socket would be unlikely to be effective against lightning.

So during a storm the only reliable protection is to unplug all the wires connecting your electronics to the wall: mains, and if applicable, ethernet cable, telephone cable and aerials. I suspect people don’t, only switching off - but then most people fortunately don’t have a direct hit on their wiring, and switching off may protect sufficiently from more distant strikes putting high voltage spikes into wiring. It sounds as if you may be located somewhere with greater risk, so unplugging may be prudent.

Regarding your speakers blowing thatvis a new one on me, and I find surprising unless the amp was powered up at the time in which case maybe effectively the lightning presented at the amp input as an extremely high level peak signal.

As you’ve learnt, purely turning off equipment isn’t sufficient. The equipment needs unplugging entirely for protection.
I briefly used a Sonos Connect playing through my old Naim 3 and I never had any issues with humming.
The only time I’ve had mumming issues was when connected un-earthed (un-grounded) video equipment such as a DVD player. Running a wire from the metal body of the DVD player to a known earth, such as the earth pin / ground pin of the UK 3-pin plug solved the issue.
My understanding is that an earth wire should be connected to the same earth / ground as the equipment is plugged into, to avoid any further problems of an earth loop / ground loop and more hum.

There could be something in your argument about lightning, in that it will, like any current, choose the easiest, most direct route it can to the ground. If the Sonos isn’t grounded, it will go elsewhere, as you appear to have found out to your cost.
Still, that is hardly a reliable strategy to avoid future damage. As already mentioned, you need to pull plugs out of the wall to provide a large enough gap that the huge current from a lightning strike cannot cross.
Remember also that lightning can enter your house through copper phone lines, and anything connected by Ethernet cables can carry this destructive current. So unplug the phone line too, along with any TV or FM aerials.

Thanks for the replies everyone. The amp was powered on at the time. I don’t think lighning can have struck our house directly otherwise I’m sure there would have been more damage, I mean more things in the house would have been damaged. The TV was on too, but no issue there.
Pulling all plugs out is not really a feasible solution - sometimes we like to listen to music when it’s raining! Sure if there’s a big storm we can do that, but in this case it was just raining.
I’m no electrician but I’m guessing exactly that ChrisSU - because the system wasn’t grounded properly the surge went through the speaker. Twice! So I’m really hoping that grounding it will prevent this from happening again.
I’ll make sure I plug in my homemade “grounding plug” to the same adaptor as the amp Blythe, thanks.

I hate to say it… but with regard to lightning surges, you might find earthing the ground could make matters of worse…
The Sonos Connect is double insulated, and so it’s internal relative ground floats by design to earth ground… but can be brought to earth potential by connection to earth or simply be default capacitively coupling. You probably will find this symbol somewhere on the Sonos which means it is double insulated.


If there is a hum on connection to an amp, it suggests perhaps you are connecting to a non floating input on an amp and it’s expecting your Sonos to be earth grounded. You can attempt to manually earth the ground, or possibly use another source input that earth grounds your amp.

The lightning probably caused one of the output transistors to short In the amp, sending large amounts of DC current straight to your speakers. That’s why your voicecoil fried.

That’s why I always unplug when a storm is threatening the area. Way too much to lose.

Indeed lightning surges can cause all sorts of unexpected issues…
Luckily in the UK all new/significantly modified compliant electrical master/consumer installations need to have surge protection included… (unless a risk assessment shows no damage can occur)

Isn’t this part of Sonos fiendish plan to brick devices and make you upgrade? :slight_smile:

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Yes Simon-in-Suffolk, the Sonos is double insulated, and from what I’ve read in other posts the Nait 5i expects it’s source to be grounded, so connecting the Sonos to ground via homemade phone>plug would seem to be a good idea. But do you really think that would make a recurrence of my power surge worse? I guessed my speaker blew up because the surge had nowhere else to go.

Would grounding help prevent that StoogeMoe? There was no storm threatening and I really can’t switch everything off every time it rains!

Well I’ve been blaming my poor fragile Nait all this time! It’s only recently I’ve begun suspecting it’s the Sonos at fault here. All this has brought hifi to the front of my mind again though and now I’m looking at an XS, new speakers … :slight_smile: Not going to happen at the moment though unfortunately.

No amount of protection will help against a lightning strike. If I see the forecast is for the possibility of thunderstorms, then everything gets unplugged. For me, that means it is usually unplugged all summer when not in use.

It’s hard to say… but if the live / neutral surge is relative to ground then potentially yes.

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