Huming Nap 250dr

My nap 250 dr produces a loud hum sound that comes and goes in waves. It’s not constant it’s rather rhythmical and at its peak it’s loud, too loud in my opinion

I just bought a used amp and the setting up at home just got a bit spoiled?

Is this amp faulty and in need of service maybe?

Any thoughts on this?

Might be DC on your grid. For me a DC Blocker made my NAP250DR dead silent.

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A quick search of previous threads will bring this up quite a lot. I have three 250DRs and three Supercaps. One of the Supercaps (the only Non DR and factory serviced three years ago) will occasionally hum loudly in the way you describe. The 250s and SCDRs are all silent. They are all on the same dedicated circuit, connected via a Grahams Hydra. I don’t believe a service will help as my noisy transformer is in a serviced unit. It’s a fact that sometimes the transformers in larger Naim amps can be noisy but it’s not consistent as my set up demonstrates. DC blocker may work, I haven’t tried, but if not it may unfortunately be a case of live with it or move the unit on. Sound quality is not affected btw.

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It’s not faulty and a service won’t change anything. It sounds like you have something somewhere that’s polluting and putting DC on your mains and your NAP250DR’s transformer is particularly sensitive to that particular type of pollution. Best is to try to track down what that might be. Things with heating elements are classic culprits, as are faulty fridges, freezers that sort of thing. Of course, it could be from a neighbour, which is tougher to fix…

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I had a similar issue with my 250DR and now to a lesser extent with my 300DR. I’ve since tracked down the intermittent humming with the 300DR being due to certain kitchen appliances running (notably our Thermomix and the dishwasher).

As already mentioned, the likely cause is an appliance in the house polluting the mains. When the amp starts loudly humming again, see if you can find an appliance running that’s drawing current.

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I’m feeling your pain @Masse. You’ve bought arguably Naim’s most iconic product (albeit used) and it’s brought you problems. I hope you are able to sort it out with some of the advice here.


Sorry to hear about that, I’ve had similar issues with my NAP200. It even went back to the distributor to have it checked, but it seems that th ehum was within the specifications.

My now 1-week old NAP250DR is absolutely silent however up till now … :smiley:

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We replaced the fridge a few months ago, its insulation was really bad. It was almost 30 yrs old. Since the fridge is replaced the hum of my supernait is much calmer. Never these peeks anymore which you describe.

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As mentioned before. If you suspect hum come from the grid say fridge, heat pumps, dimmers, washing machines, whatever, then a DC Blocker will most likely sort this problem for you. I got myself a Supra DC Blocker for 200USD used including the cable. It went from buzzing a lot to total silence. So worth it!


In a previous house a DC blocker from Isol-8 did the same job. That one was a bit more expensive, but still it was a great relief when the hum was gone…

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Will try dc blocker and run this at my parents in law over a gt or two - thx for all the help guys.

Got me in a good mood actually. So most here thinks it’s a grid/mains issue - can be fixed then!!

It’s a shame cause now I worry about this instead of enjoying the breath taking sound the machines has. Having upgraded super units to Nac n272 and nap250 dr with a nice lil. Chord signature tuned Aray in between

Tried to locate anything within the house without luck.

The seller used a dc blocker. Decent guy and will let me in for a test his house.


A dealer nearby had a demo unit. So I had the DC blocker at home for a week to establish whether the Isol-8 unit fixes the problem, and without compromising sound quality. Maybe you have a helpful dealer nearby too?

Iiiiottttttttt woooooooorks!!!

Supra DC blocker makes my power grid to shut the f… up!!!

Thx for all you valuable input guys.

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Great — congratulations. Enjoy the music without hummmmmm… :smiley:

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Magic product. Should be included with all Naim sold amps :sunglasses:

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And what a magic combo nac272 and nap250dr (chord signature tuned aray in between) - i enjoyed my SU but this is something else. Separation, control and pure joy. I am so happy playing my fellow swede Daniel Norgren on this system

A great como it is indeed, what speakers are you using?

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Yes don’t underestimate what that chord cable does
When I was using one …I felt it was one of the single biggest improvements I made … though £825 is a fair chunk of money for a single cable…

I did mate:-) thx pall

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Audiovector sr3 signature