All transformers hum. AC 50-60hz means voltage is changing polarity 50-60 times per second this is amplified in a transformers very long copper windings better isolation between the transformer and whatever its mounted on solves the problem. The transformer will still hum but you won’t here it if its isolated properly
…then your last sentence poses an obvious question.
When my transformers hum, they all do. 2 Hicaps,555psu and the 2 big ones ( 1300VA each ) in my MF power amp.
The ifi things help to reduce the hum. Ive always put it down to dirty mains ( my Samsung fridge in particular).
My mains voltage tends to be about 230v when they are humming.
Best solution is to turn the 282 to 10 O’clock.
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what does it mean exactly “turn the 282 on 10 o’clock”?
Turn the Volume on the 282 to 10 o’clock.
(9 o’clock being 90 degrees clockwise)
Not The Same As Eleven…
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What’s 282?
A very, very popular Naim pre-amp.
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ah ok, as if to say: the higher the volume, less the buzz is heard!
Indeed 
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Have always assumed over voltage was my issue. Measured it at 244 to 250. Then stopped worrying about.
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If overvoltage caused the humming, that would be easy for naim to fix ? Just specify a transfomer for say 260V.
I’ve previously stated that my two NAP 250s hummed, albeit, one louder than the other.
As we left the kit on 24/7, you could hear them from the sofa when no music was playing. The hum was cured by using two iFI DC Blockers.
Did not stop it 100%, but you now had to put your ear right up to them to hear, so a good result.
Never did find the cause, the line voltage was stable at 236 VAC. The Hi-Fi was on its own dedicated supply which was tested by turning everything else off, then back on trying to find the cause. But, the hum was always there.
The hum wasn’t there from the start, it developed over time. I put it down to external factors; lot of people having Solar Panels fitted as the local council was doing a deal. Also, near us two railway lines being constructed. EWR and HS2, so quite a bit of civil engineering and electrical work going on.
Now that I’ve changed to the Linn Selekt DSM; Edition Hum with its SMPS PS and the Chord EE8 with its SMPS PS all is quiet.
DG…
I assume that’s a joke.
Transformers must confirm to the nominal voltage with a specific +/-% acceptable range either side of that. That varies from country to country but it’s about 10%. The UK is not bang on 10% if I recall correctly but for the purpose of this explanation let’s assume it’s 10%. That would give a 230v unit a compliance range of 217v - 253v. Of course, whether something hums or not is not part of the compliance qualification. 260v would operate from 234v to 286v which would be uncertifiable.
Last I heard, Naim’s units are tolerant to +/-12% either way which is more than is required in most regions.
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Due to an incorrect local substation tapping, my original Naim gear was on 260V for near on 20 years before I noticed it and got it down <250V. No effect on my gear, other than a slightly less of a hum after the change, but not solvent, presumably due to all the other humming reasons.
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