Question re dreaded hum


I’ve got a 272, XPS DR & 250 DR. A few months after purchase the XPS developed a very distracting hum. Eventually I swapped it for my dealers 6 month old demo unit which was silent. Now a few months later another hum has appeared.

How are hums appearing months after install? Particularly weird given one of the units was a demo unit ie not new.

I had previously experimented with plugging in the units direct to the wall or into a Wireworld Matrix but no difference. Dedicated mains is not an option - I would consider something like an Audioquest Niagra if I had to but I’m intrigued as to why this is occurring after a few months rather than almost immediately.

It will be something local to you - either in your house or in your immediate neighbourhood that is the cause. The transformers are just reacting to it. Take it back to your dealer and it may well be fine there. First try tracking down what may be the cause. Things with heating elements can be notorious for causing toroidal transformer hum, so if it only occurs in winter months then things like electric blankets, water heaters, electric fires, etc… are likely culprits. Hairdryers are also likely culprits but luckily they are usually only used in short periods of time.

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Just dirty mains, it will probably go as quick as it came.

Wow I didn’t know, I thought the transformer hum is just random. Sometimes I go and put my ears next to the amps and I can hear it. Then sometimes I don’t hear it.

It will be caused by something. It’s usually due to something putting DC on the mains supply.

Interesting. Next few weeks I’m gonna test out a power conditioner myself, gonna see what does it effect.

The first thing I would do it wait until the hum starts, then turn off appliances in your home to see if you can identify the culprit. It could be a light fitting, heating pump, fridge, TV box etc.
It’s also possible that it could be an appliance in a neighbours house, or a nearby industrial unit, which becomes much harder to diagnose.

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My NAIM system is running on a dedicated circuit, a line not shared with any neighbor or appliances and yet my Flatcaps hum. My previous amp, a QUAD 405, in the same house and circuit was dead quiet. It is time for NAIM to recognize and address the wide spread problem of mechanical noise which is not common with other manufacturers. Stop blaming the poor neighbors.


My system is on a dedicated circuit but sometimes it still hums, sometimes not. I have not been able to track down anything particular which might be the culprit.
I’ve had the same issue in 3 different houses over the past 20 odd years.
I usually just turn up the music a little then I no longer hear any hum.
Some people report that although a mains conditioner might reduce the hum, they can also “suck the life” out of the music.
Be careful not to trade a silent transformer for potentially inferior sound quality.

I’m running with Naim now for some 13 years. Started with NAP200. Then NAP250 and now NAP300DR.
Also running with 2 Hicaps and 2 XPS, one of them DR. Never,ever had something that even remotely sounded like hum as here described. Only hum I heard was myself humming with the music… :smiley:
No special power cords, no special power circuit. Everything just standard. Am I just lucky or…?
And,forgot to add, my home is in an appartment building. So lots of neighbours with a variety of appliances.

The Quad 405 has a conventional transformer, not the toroidal design that Naim uses for SQ reasons. That’s why Quad power amplifiers don’t hum whatever the mains is doing.



I would just ignore it, as in my nearly 50 years of experience, it will never go away, but it doesn’t seem to affect the sound of the music to any great extent. There are plenty more important things to concentrate on. I would also offer that in my experience ‘mains conditioners’ make matters worse, even if they manage to reduce or silence the hum.
Just grin and bear it!

Unless the conditioner has an internal balancing transformer, removing dc offset is something it’s unlikely to help with.

A balanced isolating transformer (preferrably non conditioning) is the way to remove dc offset which is the most common cause of hum.

I’d strongly suggest doing root cause analysis before spending money on a “solution”. A multimeter in DC mode can tell you whether there is DC on the mains - though an electrician with oscillascope can tell you what its doing to the waveform. Get the problem identified and target a solution for just that problem.

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Yesterday, I went to the shop to get my broken Nap 110 back. I asked the branch manager about power conditioner since I don’t have one. He explained about them to me and he recommended me the MS HD Power MS-1080P V3. The shop uses them and he told me that he did not hear any degradation of sound but instead improvements.

That might be true but they can only address a subset of mains issues. If yours isn’t addressed, it might cost money and not resolve the issue. You might get lucky of course but all I’m saying is do root cause analysis before choosing a solution.

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