This is the sound of my nap 180 humming, phone next to the position of the transformer.
My hicap is also humming as loud as the power amp
If both boxes are doing it, sounds like you have some serious issues with your mains supply. Time to narrow it down with a bit of detective work, I think.
After few minutes it stopped humming that loud and it went into the normal hum volume
Blimey. How close was the phone?
Makes my SC2 hum seem trivial…
Strange (to me, a technical numpty) cyclical effect too? My SC2 is just a constant pitch hum, not that kind of noise at all, and fairly easy to ignore…
Then it’s likely to be a bad appliance somewhere on your mains, or possibly a neighbors, that is switching on and off.
Tmr I’m shutting it off since I’m not in my house for a few days, after that Im going to buy a power conditioner for my naim. My friends said that it is a coil whine which is not good
Basically next to it
I would want to track down the source of the problem rather than spending money on something that just gives symptomatic relief. It could be a cheap appliance like a hairdryer that is easily fixed or replaced.
Is it possible that air conditioner can affect the transformer? Because nobody is using a hairdryer
I just tried recording my SC2 hum, phone barely picked it up. Which did surprise me, as it is audible. Maybe I’m doing it wrong.
Hahaha, sometimes the transformer doesn’t hum at all. Fully silence
When the hum starts, try turning everything else in the house off. See if it stops. Then turn things on one at a time and you should find what’s doing it. You could then put a DC blocker on that item.
Alright, will do 
. I guess it is the air conditioner or my fridge. Because those are the only thing switched on besides the lights
Yes, it’s possible. Try to identify the source by switching off Individual devices or circuits. How far away are your closest neighbours? It could be a faulty appliance in their house. Also nearby industrial premises, arc welders, farm buildings, etc. could be the source.
I live in a terrace house, safe to say that they are next to me. I’m not near to any industrial premises aswell, no arc wielded or anything
The things that degrade mains draw non linear current , basically anything with a non resistive load such as motors and power supplies!
Phil
Oh, then I think it is safe to say that both my fridge and air conditioner caused that loud hum
Even more powerful than the fridge.
I really do need to get a power conditioner for the naim now
Dedicated radial mains first