Hum in New Classic


I understood that the new classic series were not supposed to hum. But mine does. The NSC222 hums but the NAP250 much more audible. Usually during daytime for some reason.

The main hum/buzz thread reads: If the “New Classic” range is put into Standby mode, there should be no hum as the toroidal transformer is not powered up.

Standby is simply off right? I can clearly hear the hum when in standby. It emits from the devices. If I disconnect the speakers I can still hear it. When I connect the preamp or power amp independently I can still hear it. The preamp being much quieter though.

Now is something wrong with the devices? It’s quite annoying since the living room also has my work desk.

Quite annoying for such expensive gear. This would really be a reason not to purchase Naim had I known in advance.

I ended up connecting the gear to an extension cord with an off switch to cut power to the entire set. Not ideal since I now have to go behind the set and manually toggle mains power back.

Hi, my 333/332/250 has by far the loudest hum of any Naim gear I’ve owned. When I have some time I will investigate it further, but if I can’t improve it, the whole lot will go.

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I wonder how much they would need cut the performance to get rid of the hum.

Or try something to get rid of it or improve something to compensate. Like Richard Dunn of NVA amps that lowered the impedance by winding the primary outside the secondary.

I hadn’t seen you’d moved back from Chord, Chris.

Humming is due to your listening environment in my experience. I had some humming with olive kit in one home. No humming with OC in my last home. No humming with OC or NC in my current home.

My NPX 300 and Uniti Nova are completely silent. But I’ve had an Uniti Atom HE that hummed very loudly. The hum made me so stressed that I could’nt enjoy the music. It seems to be a lottery whether you get a silent unit or not. Very strange that Naim will not fix the problem.

I’m pretty sure I read there were steps taken for NC to reduce hum. Different transformers and how they are mounted.

If that’s supposed to be the case it certainly didn’t work for me. My last all-Naim system was NDX2/282/250DR and only the 250 hummed. Not ideal, but it was bearable. With the 333/332/250 all 3 boxes hum, at 3 different frequencies. In quiet passages of music it’s clearly audible.

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I don’t think it is when the switch on rear of 250 is set to instant on if this is the case try the other way “auto standby”. When in auto standby toroidals should be off and equipment is powered by SMPS only to should be silent. If this is not the case you don’t have a toroidal hum issue so must be something else.
With regard to reducing transformer hum a power conditioner (Puritan Audio Laboratories) was most effective for me and had the happy coincidence of improving SQ but YMMV.


My NAC 332 and 2 x NAP 350 are hum free.

I have 4 NC250s along with all the other gubbins to run an active system . I do not and have never suffered from buzz or hum from Naim gear that was anything more than being able to tell item is on with ear close or on the item . I’ve had supercaps, classic 250.2s NDX NDac ,Nait50 Nap300 here in last month’s .Non of them hummed , now that can’t be luck.
The only way I can make them make noise is if I put on a hairdryer in house . I do get a very perceivable reduction in quality of sound when we use the induction hob .
But the the new NC250s take things to a new level of quietness ,they are definitely a step better . It’s hard to believe they are actually on.
But I have to say surely surely if any hum is present once the music is playing it won’t be apparent .
I think if you are near industry or in a more congested environment etc you definitely more exposed to potential nasties

My 300 series did hum a lot. A Puritan PSM156 cured it without any detriment to sound quality. Without the 156 a hair drier would cause hum but not with the 156. Obviously your situation may be different but worth taking a trial if possible.

My hum pointed to dc on the mains (changed loudness sometimes) so the dc blocker on the 156 helped this. Other interference was helped by the circuitry within the 156.


My NPX 300 is as I earlier said silent 5-10 seconds after powered it up, in the exact same socket where the Atom HE hummed so loud that it was heard in quieter parts of the music. Very frustrating! If my NSS 333 hum I don’t know as I all have it powered up by the NPX 300. I also had a NDX 2 and a XPSDR which was completely silent. My Nova is also dead quiet. But it seems to me hum or silent is a.lottery.

Humming is caused by DC on the mains. This comes from pollution of the supply from domestic or industrial motor driven devices. It will vary with use of these devices. A power conditioner is the solution.
There’s a really good discussion by Steve Huff.

That’s not strictly accurate. DC offset is not DC on the AC mains. It’s an asymmetric sinewave like +60v against -50v

In addition hum has several causes of which DC offset is not only one but not the most common. Over voltage beyond the transformer’s tolerance is generally no.1. Which is why getting a DC blocker before diagnosis is a bit of a gamble.

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You may be right about over voltage but it was not my experience.
My voltage was running between 248 to 253, so got a step down device installed which in itself works well (now between 223 and 228), however, the gear still hummed like a b’stard.
That said I do think my mains are particularly poor but getting a power conditioner that effectively tackled DC on mains/DC offset, vibration reduction and rebalanced AC sine wave whilst improving SQ was the real deal.
As with everything YMMV.

I have fought hum for years with different DC blockers in different systems. Puritan 156 finally made my boxes and sound relax. Silence! A humming transformer is a sad transformer not performing at its best. They get saturated.

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I have never understood why it is necessary to adapt the electrical system of a house to an amplification. The same thing happened to me with an XS2 I busted. tried on various sockets and in various homes always the same problem. from that day I understood that if I want to buy a Naim I must first try it at home.

I wonder how much they would need cut the performance to get rid of the hum.

Is that really a thing? Is that an actual tradeoff? Only since I discovered Naim hum vs performance is mentioned as a tradeoff.

In any case I am not much wiser on what is the cause and what I could do. Hum while the decivces are off? That seems weird. I can understand hum when on but not when off. I mailed Naim support and am curious what they will say.

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While my 222 and 250 are quiet(er) they do hum occasionally and fairly softly. They are improved but I believe fundamentally the design philosophy has not changed - and looks like for a good reason. The below has been a good succinct reference for me and something on filtering and DC blockers in there too. I’ve not tried DC blockers but it’s my own experience with filtering mains blocks for sure.