It was from the transformer.
1 Like
Actually I think @drago had to change his fridge because the old one broke and he was very anxious when choosing the new one that it might affect sound quality in some adverse way. But as far as I remember, he told us later that it had no effect on sound quality at all.
3 Likes
It was different - I was cautious when changing fridge.
My boxes are also random when it comes to Transformer hum. 2x 555ps and 500ps no hum. 552ps hums frequently- sometimes really loud. But it stops after a while āwhen dc noise is goneā.
One olive supercap humming - the other dead silent.
2 Likes
No hum whatsoever on my NC gear.
I have a NC system and hum is not an issue. Nor was it with my OC gear. However the hum may still be there are we may not be aware of it. We live on the approach to the Brooklyn Bridge. There is a lot of ambient noise. The price we pay for our skyline view. We do however, try to mitigate low level vibrations with good racks. For us, low level vibrations are more the issue. There is a subway line running under ground. Also low level vibrations from bridge traffic.
2 Likes
To hum or not to hum . That is the question. Maybe I should find a suitable Fridge forum (apologies if anyone here is already on a fridge forum).
Clearly mains play a bigger role than I ever imagined.
My hum thankfully doesnāt affect the 333 or 50 baring a slight one due to very old Rega on phono.
In my ex appartment my 555 dr was starting to hum when the area ( neighboors, schoolsā¦.) were awaking, so around 7h00 am
I think we all know know the main reasons why some units hums and some donāt (see below), however I donāt think that explains why the variation of hums within the same house. E.g. I have two HiCap DRās with slightly different hum volumes. My 555DR hums louder than my NAP250Olive. You would expect some consistency wouldnāt you?
1 Like
This is what happened 
1 Like
My NSS333/NPX300 and NAC332 and 250 are completely silent even if you put your ear right up against them. My SN2 has always been very quiet as well. My Leema Acoustics Hydra 2 always has a nice warm transformer hum that you could start hearing about 2-3ā away, especially when you first turn it on and energize the large transformers. This never bothered me at all though because when you turn up the volume, youāre just extremely thankful for the clean, powerful effortless sound you get from them.
I should also note though that Iām on an acreage and the power seems pretty clean. I have no separate mains just using standard house wired outlets.
Mine is silent. Occasionally my 222 hums a little, but itās not all the time.
My 272/XPS used to hum a little bit if I put my ears close to the XPS. However, the 333 and 332 are totally silent, hum and hiss free.
No hum whatsoever here 
. (222, 300, 250)
ATB, J
1 Like
Most interesting (to me) is if people have moved from humming OC to non humming NC. But it seems like itās all over the place so no conclusion can be drawn. Itās a hum lottery
2 Likes
Indeed not an issue confined to Naim: have heard other brands of amp hum loudly. With amps having torroidal transformers the cause is almost always the mains, the hum being a symptom, and either a DC blocker or a balanced transformer is usually a good solution, though sometimes the origin can be traced to something else on the mains, when fixing that resolves the issue.
Switch mode power supplies are immune I believeā¦
1 Like
The strange thing in this is not all Naim boxes hum not even if they are same model if in a system with dirty AC. That makes me think either there is tolerances on transformers that is too big or something happens with time like parts of transformer getting lose.
1 Like
I found a service didnāt change anything as far as hum goes, and i guess why would it as the transformer isnāt touched at all in a service.
I think XPSs had a bit of a reputation for humming. It was the only Naim box Iāve had that hummed audibly throughout the room it was in and the only one my long-suffering wife complained about. Wasnāt too sad to see it leave our house.
Roger
I had a Supernait 3 which was pretty quiet. I upgraded to a NC 222/Nap250 which I returned due to loud transformer hum. I checked the replacement unit at the dealer - it was completely silent there, but still audible and distracting in my house. Dedicated mains helped the sound overall but made no difference to the transformer noise. I eventually bought a Puritan mains conditioner which fixed the noise completely.
2 Likes
Apologies from repeating this on other threads, but I really cant understand why someone hasnāt put together a small plug-in device that measures DC Bias on your Mains. The dealers would loan this out, and potentially sell more gear as a result.