The buzzing sound is still considered normal on the Naim NAP-140


I’m curious about how much noise or hum is allowed on the Naim NAP 140 or any other power amplifier (other than the NAP 140) in decibels?

hum in the condition that the amplifier makes no sound at all / idle, or there is no sound at all from the loudspeaker.

If it measures 26-30 dB, can it still be said to be normal and does not interfere with the sound that comes out when the music starts?

thank you

I’ve tried a sound app on my phone, and with the Mic 1 inch away from the middle of the front panel of my NAP250 it measures 39-42 when switched on, and 32 when off. I dont know how accurate it is though, and I find this level acceptable, but wouldn’t want any more.

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mine on NAP-140 measured 25-30 dB at about 1 inch away from NAP-140, is it acceptable?

I would consider anything above 30db quite loud for a hifi environment, that means it’s noticeable from 8-10ft away in a quiet room. On lower listening volumes that would probably interfere with smaller details in the music.

(30db is roughly the volume of a whisper)


As the Naim amp manual states, transformer hum does not interfere with audio quality. (Except when excessive).

26- 30 seems reasonable, but what is your room background level?

At the moment in my room I have maybe around 25 dB with the phone approx. 1 inch away from the transformer side of 300PS, SC, and 555PS, respectively. Which is, in my measuring app, not really distinguishable from the background room noise level when anywhere else in the room (coming from my breathing and whatnot). There is only a barely audible transformer hum with my ear 10 cm away from the PS.

However, occasionally the mains is less clean and hum is louder, but still barely audible when 3 meters away from the PSes.

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There is no hum at all from my Nap 140, not a sound.

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That sounds acceptable - once it’s turned on.


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Apart from a service in 2017 it’s hardly been turned off in 24 years!

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It depends on the mains largely, though as others mentioned, not every unit is the same

A buzzing noise from the toroidal transformer is almost certainly due to your mains supply being sub-par, probably due to the presence of DC, especially if it varies from time to time, coming on and stopping or changing suddenly. It may come from something in your nome, in which case you could try to track down and eliminate the cause, or it could be on the incoming mains in which case you are stuck with it. Other than identifying and fixing the source, the cure is to insert a DC blocker in the mains feed.

Do you listen to your music 1 inch from your NAP140? If so, the noise level is unacceptable.

As a guide, if you hear the buzz from your listening position, it will annoy you and so is unacceptable. If you can’t, then don’t worry.

Hope this helps, BF


yes I think your explanation makes perfect sense.
I feel a buzz when my ear puts it very close to the case of the NAP 140, sometimes I stick it to the case
But even at a distance of 1 meter, it can’t be heard.

from what distance are you listening?

I am sat about 3.5 metres away but there is no hum even up close

Yes, but using DC blocking filters not quite familiar here

What parts of the NAP-140 should we check after years of use that could possibly be the source of hum?
Does the NAP-140 toroidal have a pad / wedge that can age over time and need to be replaced?

I’m not sure that there really is a problem?

All transformers vibrate. It’s unavoidable, due to the way they work. The vibrations get louder when dc on the mains pushes the transformer into saturation. The reason it’s not usually a problem is because transformers work counterintuitively and actually desaturate when passing current. It’s even possible that the noisy transformer will sound better than a quiet one due to it desaturating into its design region, whereas a quiet transformer could desaturate below its design flux. However, as has been mentioned, an excessively vibrating transformer is not good and may indicate a severe mains problem or a problem with the transformer. A sound level below 30dB is perfectly acceptable though. In my listening room, this would be below the rooms noise floor!


thank you this information really helped me in understanding the vibrations on the NAP140 even though it is small, the possibility could be from my bad AC voltage, I want to know more about the DC Blocker, what shape is it and is there a link that explains this?

thank you

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