Nova Transformer Hum

Hi Folks, my first post here. I have just bought a Nova which, whilst delivering a wonderful listening experience, has serious transformer hum. It’s loud enough to hear between tracks sitting 8-10 feet away and when all else its quiet I can hear it at my desk 20 feet away. Having searched this forum I am astonished to discover this is not an uncommon problem. Is this a design fault or a Quality Assurance problem and does anyone from Naim acknowledge the issue? The Nova is a £4k+ piece of high end audio equipment that hums like a cheap bathroom light with a shaver socket. It seems like the general advice here is to get it replaced and hope you get a good one. Having owned Naim kit for decades I am rather disappointed to say the least.

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How it’s connected? Also to a tv?

Yes, it’s connected to a TV, CD transport and Naim phono stage but it hums with everything disconnected and me holding it in mid-air.

Is it just the transformer humming or is it a hum that’s coming through the system speakers.

If just transformer hum then it usually indicates something on the mains that is the cause. All the transformers are individuals here so while some may be quiet to one particular problem, other may well hum to a greater or lesser extent to the same mains issue.

All transformers are tested for hum levels both at Nuvtem and at the Naim factory. Of course, it’s impossible to be exhaustive and a serious mains issue could still cause a tx to hum, which would otherwise be quiet elsewhere or with different mains pollution issues.

Is the transformer hum constant or does it vary depending on the time of day?

You need to confirm it is not a mains supply issue (DC or noise on the supply) first. Try plugging it in (no other connections or speakers) in another room, but ideally in another property. If the transformer is still humming then return it for repair.

Hi, thanks for your response. Just the transformer, nothing through the speakers and it’s constant with no variation with time of day. If it’s a mains issue why does it not effect other equipment in the house, Naim, Primare…

Thanks. Tried all that, still hums! It’s going back. As I said in my original post I am surprised by how many people report this problem. I’m no expert but I thought toroidal transformers were meant to be resistant to vibration by design.

The one weakness of toroidal transformers is that they can hum when presented with DC or other mains artefacts. The irony is that Naim have found that the higher the quality of steel used, the better the performance, but unfortunately the more prone to hum from mains artefacts. There’s a lot that has been written here about the enormous lengths Naim go to in order to try to minimise this (and lots of work in the past and current with Nuvotem looking at ways to try to minimise without impairing the SQ) - however, Naim will not compromise performance so they steel quality remains as high as possible.

I would suggest you contact your dealer and explain the issue with them. Perhaps they can lend you their demo unit to try on your mains, and they could try yours at theirs.

Thanks Richard. My dealer is going to lend me a demo unit to try here. Is there a sequence to go through in order to identify any possible “DC or other mains artefacts.”? And can you recommend any suitable fixes, conditioners, purifiers or whatever? Cheers.

You need to turn off every single other electrical thing in your house. Hopefully the hum stops. Then you turn things on until you find what is causing the hum. Of course, if with everything off the hum continues, this won’t help. You want to avoid any mains filtering etc wherever possible.

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Beyond what HH writes above, if there’s a source of DC on your mains that you cannot identify (maybe from some other local device from a neighbour) then a DC blocker may help. Of course, each tx may respond slightly differently to the next, so what might upset one with hum, might show no hum with another, and vice versa should it be a slightly different artefact.

We had / have a weird one now solved. Noticeable transformer buzz from the 250 on and off. Exactly what HH mentioned. We went room by room switching everything off, till nothing left. Then it came back, it was our daughters hair straighteners ! Can only assume they are electrically polluting devices.

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If it’s humming you won’t be getting the best performance in other areas either. When a toroidal hums due to DC offset, the core often saturates and they produce more EMI than their derided EI block transformer cousins.

A multimeter in DC mode can also give you a quick indication of any offset. It should read near zero. Though more elaborate equipment is needed to provide more detailed information.

I’d return it and request a replacement, it’ll drive you bonkers. My first SN3 hummed like a mad thing and I tested it in 3 different houses, it’s replacement was and still is completely silent.

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Get a DC blocker like Supra DC Blocker and problem solved. It’s new around 300GBP. Should be included with all Naim products :wink: Never heard of equipment so sensitive to DC on the grid. I assume most other have build in electronics to prevent it.

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Perhaps she needs a haircut :wink:

Seriously, no, she should come first!

How often and for how long are they in use?

Last year Mrs AC decided she wanted some fancy Dyson hair gadget for our daughter’s birthday - I think it was £500 for the set :scream:

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As Naim have discovered, it’s relatively easy to make a toroidal transformer that is less susceptible to hum from mains artefacts - much cheaper too! The problem is, they just don’t sound anywhere near as good. When I was at Naim we regularly had samples in for listening tests. I guess it was always tempting to make the compromise for a much easier life, but compromising sound performance is just not the Naim way, so…

All I can say is my system sound far better with a DC Blocker in line relaxing the transformer from external noise. In today’s world noise on the AC grid becomes more and more common and my hopes would be that naim could protect the user from a bad experience in a greater way because we don’t have lab environments in our homes and things have changed past 40 years. Sometimes an idea need to change when things around it does.

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I’d strongly advise to OP to accurately diagnose the root cause before spending money. If the cause turns out to not be DC offset, they are likely to get more annoyed than they are already. Accurately diagnose the issue, then find a targetted solution.

GHD I think, we actually got her to turn them on and off to prove the point. It definitely was proven, very buzzy power amp when on. We know those Dyson products BTW she now works there :wink:

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