Mains induced crackling

My son alerted me to a crackling sound coming from his speakers and also his (very cheap USB powered) soundbar.
Had a listen and yes it was also present on my system though to a much lesser volume, you really had to be ear to the tweeter to hear it.

First off I suggested that he work through the house turning off things and see if he could identify what was the cause. No joy.

Next we waited until Mrs Willy was offsite (she’d get withdrawal symptoms if she lost her podcasts) and did some more invasive testing. Using my system as the monitor (it’s on a separate consumer unit) we tripped the RCD for all the sockets. Silence.
Then we reset the RCD and individually switched off the breakers for the separate mains rings. Even with all these turned off the crackle was still there. With the individual circuits still off we then tripped the RCD and the noise disappeared.

Repeated all multiple time to double check we got the same outcome.

Any thoughts on what might be the issue?

Could the RCD itself be faulty/noisy?




I would get a qualified electric to check and test it. RCDs are not expensive.

Could also be a loose connection.

Better to be safe than sorry.



Almost certainly it’s mains earth contamination. A balanced power supply won’t block that.

I’ve heard this before when connecting my Luxman amp using a three pronged earthed mains lead (Luxman recommend non earthed for their kit) and sure enough the problem vanished when using unearthed. That’s just background info. We can’t do that with Naim systems, though it should be possible to lift the signal ground somewhere.

Problem with mains earth is it can span circuits so shutting of things at the CU doesn’t break any earth connections. And if the property is shared, there could be a lot of contamination from outside the home too.

An electrician is your best bet.

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You’ve done some good diagnostic there, well done. Definitely get an electrician in. If you just have one RCD, then it likely your Consumer Unit is quite old, and therefore your RCD is quite old. Due to the number of cheap plug in power supplies (e.g. for USB/Phones) and computers that people have these days, the old type RCD will not trip as quickly as they should, so newer RCD’s have been improved to trip better - so certainly wouldn’t harm to get it changed. It sounds like you can quickly test it anyway, which is always good.

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Pork in the electric oven. :wink:


On reflection I don’t think it can be mains earth contamination.

My son’s sound bar is powered off a usb wall wart and has no connection to the mains earth yet is the most affected by the “crackling”.

Tripping the RCD stops the “crackling” but I don’t think it disconnects the mains earth?


What you appear to have is Interference which is being conducted along some part of the Mains wiring (not just the Earth wire).

Remember neutral is also earth.

Is the sparky coming round to have a look for you? I’m sure they’ll suss it in no time.

I’ll get the sparky in, it’ll be a few weeks as everything is starting to close down for holidays.
Other consideration is i need to track a ceiling for wiring in a retrofit of smoke and co alarms as part of the building control approval for the new kitchen. Would be an idea to get that done at the same time.