A Starting Guide to Naim Hum/Buzz

To add my latest on the infamous Naim transformer hum story.

Re Over Voltage
For the UK, the supply to your house should be 230V +10% -6%. That means a maximum high of 253V
My house supply voltage has always been very high, I’ve measured from 248v up to 252v.
All my Naim transformers have hummed, some worse than others. That was compounded by a neighbour on the same phase causing DC offset. To help with this I designed & built a blocking filter, it fixed the annoying DC offset causing a changing hum/buzz tone & volume, but not the constant hum from the transformers; that was some 10 years ago.
A few weeks ago the electric cmpy reset the supply voltage & I now have between 238v & 240v.
The Naim hum is now almost inaudible.

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What if the voltage drops bit low. Same issue as bit to high?

My XPSDR hum even with a DC blocker before it. The 300DR PS is dead silent. Strange.

No, low voltage is not the same.
Its not strange to have different transformers having different hum results, any/all transformers will be different.

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My XPS was the only one (of several) Naim boxes that hummed significantly. This was both before and after it went to be upgraded to DR.


I believe I’ve read here the XPS is the worst of Naim products in terms of hum. How about the 555PS?

Have read it varies by individual unit. The following is just my personal experience of transformer hum on the Naim kit I’ve tried:

  • Nait 1 (no hum)
  • Nait 2, olive (no hum)
  • Nait 3 (no hum)
  • NAP 140 (slight hum, audible from a few inches)
  • HiCap, olive (loud hum, audible from at least a metre)
  • SuperNait (no hum)
  • SuperNait 2 (hum, audible from a foot)

Unfortunately the HiCap I still own, and really want to use, but I can’t go more than a few hours before taking it out. Have tried a DC blocker to no avail. It does get slightly better after it’s been plugged in for a while, but not enough.

I had same experience between SN1 and 2.

You may have read this but our experience has been that our 555PS hummed considerably more loudly than its predecessor (an XPS2), our olive supercap or our NAP135s.

The 555PS hum was stopped by inclusion of a balanced power supply in the mains supply radial for the hifi.


Best regards, BF


This is a very interesting opinion, because it is difficult to describe it in words from our hearing on the hum in the amplifier / PSU unit, then how many decibels can it be said is still normal from the hum sound on the Naim / PSU Naim power amplifier?

thank you

Some people have reported where they have several PSU’s, they all hummed to different amounts. My original HiCap and NAP140 were different, and others may have two different NAP250’s with different hum volumes. In the end I think you just have to decide on whether the hum interferes with the music (which is probably unlikely) or is too noticeable and therefore disturbing when there is no other sound in the room. I now have a silent HiCap DR and a bearable humming NAP250.

Out of interest I did record my humming HiCap and it looked like the picture below - but then I wasn’t really sure what this was telling me


if I measure my NAP-140 with decibel meter on the top of NAP-140 casing, it measured 25-30 dB, is it normal?

I’m not aware of any specification, but it sound quieter than mine

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:thinking::thinking::thinking: how many more times is this going to be asked :pleading_face::pleading_face::woozy_face::woozy_face::face_with_raised_eyebrow::face_with_raised_eyebrow:



thank you for replying and sharing.
maybe my room is too quiet, and so the smallest sound will be heared…

from a Audio Science Knowledge perspective, is there any table/information that explain how many decible that still allowed for a audio power amplifier hum ?

Of course not. The simple answer is, if it bothers you from the listening position then it is too much. Bear in mind transformers hum loudly when their core is saturated. So all the low EMI benefits of a toroid go out the window if it has been put into a saturation state.

But the solutions are pretty straightforward. I’m always amazed when people suffer the problem and put up with it because they take Naim’s view on power conditioners to extremes. Their view is not “thou shalt never ever use a power conditioner under any circumstances”. Though most seem to interpret it as such. Their view is closer to “If it ain’t broke don’t fix it”. Or more specifically, if you don’t have a specific audible problem with the mains that you are trying to resolve, then a power conditioner will likely sound worse.

Clearly if you have a hum, and it’s bothering you, then tackling that would be the lesser of two evils. However, (and this is important) don’t just throw a generic power conditioner at the problem. Get a sparky to measure and tell you what is wrong with your mains and buy a device just for (and only for) that issue. In the case of hum, 90% of the time it is DC offset which can resolved by a balanced power transformer and no mains conditioning at all.

Too often people advocate a conditioner based on the impact it had on their system. But their mains are not your mains and their hum isn’t your hum. Specific solutions for specific problems is key.

And if you buy a device and it helps, you can stop using it if you move and no longer need it.


We have three power supplies (with another on the way) on a dedicated mains spur sitting on Naim Fraim that all hum to some extent but the NAC552 power supply is very noticeable and can be heard from across the room. If we ever get entertain in this room again they will have to be switch off when no music is playing as they are very distracting.

My Naim dealer has suggested putting pads of some description internally under the power supplies transformers which has apparently previously worked. Due to the current situation I’m still waiting for this retrofit. Has anyone else had this done with success?

If noisy Naim power supplies are still within their warranties is there an option to return to base for help as I feel like I’m treating the symptoms rather than the cause here. Is there some official response from Naim, perhaps @Naim.Marketing could step in and offer suggestions as to what is deemed acceptable ?

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Instead of tolerating something so annoying, why not consider installing a balanced power supply on your dedicated radial? If you are in the UK, a call to Airlink Transformers should sort you out. Many owners of Naim systems have done the same.

Best regards, BF

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This suggestion seems to indicate that the dealer doesn’t understand that a loudly buzxung transformer is a saturated transformer and the ill effects it has on the performance of other units goes beyond a humming noise and into EMI.

Just get your sparky to tell you what your mains abnormalities are and tackle just that problem.

Worth noting, before I joined the forum, I’d never heard of a humming Naim transformer. Certainly never had it on any of my 8 boxes that use toroids.


Hi @Bluesfan, I appreciate your comments and this may be what has to happen. I’m just wondering how far we have to go to get something to work. As not all power supplies hum on the same spur should this be considered a fault in those that do?

Hi @feeling_zen, this is the point really, not all power supplies experience this issue, we have three, one is very noisy.