Poll; Have you ever experienced Naim Transformer Hum?

I don’t know what kind of technical feedback there can be but I bring my experience here.
Respecting the correct sequence of power on, before the hicap and after the nap250, waiting about 5-10 between one and the other, the hum that is usually audible from the hicap is almost equal to 0.

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I have read this a few times but I can’t get my head around it! What order do you power on in?


I power on the hicap and after 10 min. The nap250

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I bought it used so maybe during shipment it shook it loose. Or maybe that’s the reason the person sold it. Maybe on the boat ride over here it worked itself loose. It was just a little loose. Just needed to be snugged down.

@StoogeMoe - Do you know when it was manufactured…?

Naim Serial Nos vs Year of Manufacture

Why wait 10 minutes? AFAIK the order with source - pre - power amp is just so to prevent any audible pops from source/pre switching reaching the speaker:


my system is made up of 62 / HC / 250. I have always turned on the HC first and immediately after the 250. I have been trying to solve the buzz due to the hicap for some time. I tried with dedicated line, mains filter, isolation systems. three days ago by pure chance I turned on the hicap and after 10 minutes (the phone had rang) the 250. I performed this test three times and the buzz of the hicap seems to have disappeared three times. Could it have been a coincidence? I don’t know, but 3 times out of 3…

Great that it worked for you - just tried it, an unfortunately no difference on my NAP250.

What happens if you don’t do this, is the buzz still gone or back?

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I do not know, I do the test tomorrow, now 12 hours after the power on continues to be very quiet

Maybe should open my humming 250DR and see If the bolt is loose. Thanks for the tip.

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My lawn mower makes noise during operation. Does this detract from its functionality? No, of course not.
My Naim gently hums, does this affect its functionality? Not to me it doesn’t - I just choose not to attentively and obsessively listen for it.
Unless Naim specifically detail that their equipment is silent in operation - and the hum doesn’t become audible during playback - I don’t see what the issue is…

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It really depends on the volume level of the hum. Certainly where music is playing, I doubt anyone can hear the hum. But the thing is, these systems are in our living rooms where many will spend a lot of the time not listening to music, and therefore if the level of Hum is high, it can be very distracting and annoying. Hence why there is so much chatter on this Forum about it.

My CD555PSU hums along merrily so much so I had prospective buyer pull out of my sale due to the
A (Naim accredited) Tech informed me all Naim toroids hum to some degree-he had no fix.
Guess just gotta live with it.


Well not quite the case thankfully, some of the items in the article below may help improve or even fix it

Grateful thanks G Man!



Hum from my Nait 5i 2 easily fixed with dedicated power supply.
Why don’t Japanese toroidal power supplys hum?

I was mulling this over whilst mowing our front lawn at the weekend.

I concluded that whilst our petrol cylinder mower did cut the grass well, a quieter mower that produced little or no emissions at the point of use would make the experience much pleasanter.

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