Humming Surround Speakers

I have a combined Atmos 7.1.4 Home Cinema and Hi-Fi. Although the Audio Visual equipment is at the opposite end of the room from the Hi-Fi, all of it is powered from a dedicated Consumer Unit. I have an Arcam 850 AV Processor and use Preamp outputs to supply the front left and right channels using my Naim amplifier via a Ground Loop Isolater and the 4 Atmos channels using a separate 4 channel amplifier. This leaves the Arcam 850 as the amplifier for left surround, right surround and the two rear surround speakers as well as the sub. Recently I have noticed hum from the four surround speakers. It does not vary with volume and persisits if I turn the volume down to zero but does go away if I use Mute. Unsurpringly more noticable on 2 channel sources.

There are a lot of cables in a confined space which my installer has cable tied within an inch of their life so not easy to experiment but does this sould like interference between mains and speaker cable or a ground loop?

Bryce - as you say this did sound like a classic ground loop issue but as you have isolated the Naim kit from the AV kit this may not be the issue. You say you have noticed hum recently which to me sounds like it’s not always been there ?. What has changed, Any new electrical kit in the house ?. Given that you have a ground loop isolator between the Naim and the AV kit, what else is connected to the Arcam and again, have you added anything else recently ?

I would suggest that getting your installer back might be the best bet as a much as i like a internet forum grounding challenge, it may be that your AV system has developed a fault and the best solution would be to call in some expertise who can get hands on with the kit if any recent additions in the house haven’t caused the hum to appear.

Pretty certain not there previously. I have changed my turntable and phono stage but the problem persists if I disscoonct. Changed a TV in a different room. Replaced a faulty Atom in a different room.

Sky Q, a BD player, Apple TV and Amazon Fire all connected to the Arcam via HDMI, all in place for some time.

Bryce - Sky Q makes me wonder if the Powerline networking (Ethernet over the mains cabling) may be an issue (worth delving into the menus and disabling) as this can cause problems (especially with low level signals such as phono stages). Otherwise it seems that nothing you’ve changed recently has made a difference so i’d be inclined to get the installer back in to investigate and find the problem.

I recently became aware of interference with my SW which I eventually pinned down to the Sky Q box. I cured it by fitting a RA Silencer adjacent (other similar devices are available!)

So I unplugged every electrical item in the room with the exception of the AV processor and the ceiling lights. For good measure I also disconnected the HDMI to the display and the phono interconnect to the Naim amp. Still hums. Does that eliminate Powerline and SkyQ as possible sources of the problem? And what does SW stand for robgr?

SW is subwoofer. In my case in bypass mode, active mode didn’t produce the interference
I would consider mains conditioning, always worth a punt anyway in my experience

If you turn off the Sky Q box (or at least go into the menu and disable it) then that rules it out as being a problem.

You mention that the hum comes from the 4 surround speakers. Are these the ones running on the separate amp - what make and model is this amp ?

I’d check the interconnect between the 850 and the 4 channel amp, just to make sure it’s plugged in ok and nothing untoward is going on here.

No, it’s the surround speakers from the 850 that hum. The 4 channels from the separate amp are unaffected.

Disconnect the 4 ch amp from the 850 - still got hum ?

If still humming disconnect all inputs (apart from optical) including Ethernet from 850 - still hum ?

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