50Hz Hum Issue with B&W ASW10CM S2 Subwoofer

Hi Naim-Community,

After multiple unsuccessful exchanges with B&W support, they referred me to Naim, hoping for a resolution to my problem.

Here’s my current situation:

Whenever I connect my B&W ASW10CM S2 subwoofer to the power supply, I hear a 50Hz hum located in my speakers. If the subwoofer is not connected, everything is silent. My suspicion is that the Naim setup is highly sensitive, and the B&W sub, which only has a two-prong power cord, lacks the necessary grounding. However, I’m puzzled because this issue did not occur in my previous old apartment, and even an electrician ruled out any problems with the electrical network.

My current setup:

  • Naim Supernait 2
  • Naim HiCap DR
  • Naim ND5 XS2
  • Chord Qutest with Sbooster
  • B&W 805 D2
  • B&W ASW10 CM S2

Interconnects: Chord Shawline Speaker cables: Audioquest Rocket 44

If any additional information is needed, I’m happy to provide it.

Looking forward to your feedback.

Best regards from Hamburg.

How is the sub connected to the hifi and what type of cable is used? Is it a proper subwoofer cable?

FWIW, Naim recommend taking a high level signal from the speakers if the sub supports it.

image

Connected the B&W Sub via Audioquest CinemaQuest RCA to the SN2.

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Sub does not supports a HL signal (cabel) connection… :confused:

Is it me or is the high level connection right there in the photograph? Bottom right. "Speaker Level In"Also, I’m not familiar with the Cinemaquest but it isn’t on their current list of subwoofer cables.

I saw one for sale as a composite video cable. Are you sure it’s a subwoofer cable?

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hmmm, good point. never thought about this section. Because the issue occurred in my new flat.

So, i have no knowledge of how to connect a biwiring B&W 805 D2 to/with the sub via HL.

Another aspect - could a damaged fuse within the sub cause the 50hz hum?

Wouldn’t think so. A damaged fuse is like to stop a unit working. That’s how they function.

Clearly you have an earth loop which can be hard to pinpoint and very situation dependent.

For subwoofers the wrong lead can be very prone to picking up AC hum if running parallel to mains but what you’ve described seems more like a true earth loop.

I’m not convinced the cable is the right one but as I mentioned, I’m not familiar with it.

A high level connection is an alternative method where instead of a aubwoofer lead from the amp, you run speaker cables from amp to speakers, and the split off another set from speakers to the sub.

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Great, great fresh way of thinking. Will try to get a new set of cables at my local dealer & report back. :slight_smile: Thank you, @feeling_zen, so much for the support so far.

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+1 here.

Any sort of mains hum is due to an earthing/grounding problem.

A different cable will not address this, unless there is something wrong with the existing cable.

Have you checked that the Phono plugs are making good contact - are they fully pushed in…? Phonos can sometimes have problems.

Is the lead you have definitely DIN to Phono - and not Phono to DIN…? Not The Same. Please check - and - ensure any other able you buy/try is correct. Cables can be either type (depends on which DIN pins are wired).

But, anyway, Naim recommend a high level connection - and your B&W Sub has these connections - marked as Speaker Level In.

Good Luck.

Well, the official Audioquest subwoofer leads do have a trailing earth connector for the amp end. It is important to ensure subwoofer cables are the right way round. Even when they don’t have a trailing lead, the screen is generally grounded only at the amp end.

But you are right, the point I was making is that although the subwoofer interconnect seems wrong, I suspect a high level speaker connection might work better. And the speaker cables that trail from speakers to sub don’t need to be same quality as from amp to speakers. They can be pretty cheap. So I’d try the cheapest possible cable to do that first to see if it solves the problem before spending on a quality subwoofer lead (which they may not need if high level works instead).

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Gets my vote. And not just for this time or situation, either. Try a cheap cable first…!!

My guess in the OP’s case, is that the B&W sub is fully floating - having no earth connection via its mains input. Connecting to a Naim amp at line level, is causing the B&W to be earthed back thru the Naim. Swapping to the high level connection should negate this. Thats what I would try, using as you suggest, some cheap speaker leads. QED 42 or 79 is they are still around, maybe. Or Linn K20.

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Haha, I was thinking 2 pole mains flex first and bare wire. Then just terminate it with spades if it works.

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:crazy_face: Yes…!!

PS. Just trying one channel, via high level, would be enough to prove the point.

There you go. A couple metres of lamp cord and the OP will have their answer. Just butcher some old appliance and total cost of solution = zero. i like it.

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I have just done this with my partners system. She wanted to have DAB radio, via her Nait.

As a DAB Tuner would expensive, she instead bought a Revo Blik DAB radio, which I noticed had outputs via Phono sockets. My ‘made-from-bits-left-over’ DIN to Phono lead was deployed to test this arrangement. Suffice to say a ‘better’ lead is now being sought as the lash up lead works so well…!

Keeping It Simple…

Thank you very much for the suggestions. I have since resolved the 50Hz ground hum. As shown in the following images, I made a DIY grounding cable with my local dealer which I connected to the power strip.

The first test, grounding the subwoofer directly (see 1 & 2), unfortunately did not lead to a positive result; instead, it introduced another, even deeper hum.

After further research, I came across the Audioquest Irish Red cable, which, as a pure subwoofer cable, has grounding at the amp end. Since the Supernait 2 has a grounding connection, I thought: if I use the line level at the amp, it will result in the B&W being grounded back through the Naim. Therefore, after connecting the DIY grounding cable to (3): tada. Silence. Problem solved.

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As a troubleshooting step that is great. As a aolution, I’d be wary. The ground on the Naim is the signal ground, not intended as a mains ground.

Grounding the common on the high level inputs wouldn’t necessarily help unless they shared a common reference with line in ground, which apparently they didn’t. Given the home brew nature I’m half expecting Richard to moderate those pics.

It does make me wonder if the mains that the Naim is connected to is properly grounded for safety in the first place. If it is, you may have got rid of hum but introduced other noise you haven’t noticed yet. I’d think the long term solution would be a dedicated sub cable and connecting that cable’s ground to your device (incidentally, what you made is also for sale at considerable cost from companies like Chord and Atlas).

Naim send their signal ground out to input grounds expecting a Naim source to act as the signal ground for the whole system. The result of your test suggests you don’t have a Naim CD player or streamer (which would provide the ground for everything connected to the Nait).

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Well done. But… I am with @feeling_zen in thinking this is a problem understanding step - not necessarily a long term remedy.

And - again as @feeling_zen suggests, perhaps the earthing of your Naim unit(s) is not of the best…? Please - do check… :thinking:

Okay, one step closer to the final solution.

What kind of further info do you need to get a better overview of my entire chain?

As already mentioned above my current setup consists of the following items:

  • Naim Supernait 2
  • Naim HiCap DR
  • Naim ND5 XS2
  • Chord Qutest with Sbooster PSU
  • Interconnects: Chord Shawline all down the way
  • B&W ASW 10CM S2 via Audioquest CinemaQuest
  • B&W 805 D2 via Audioquest Rocket 44