Buzzing PS555DR - intermittent

No damage, also no guarantee the dedicated circuit will eliminate it.


It seems to be totally random with Naim products what hum and don’t. Not sure why it is like that. My 300DR PS is dead silent. My XPSDR hummed quite some. My 555PSDR is dead silent. My Supernait 1 hummed, my SN2 never did, my SN3 did, my 250DR did.

All behind the same DC Blocker.

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Forgive my ignorance but what form does the DC blocker take?

DC on the grid most often make toroid transformers go bit bananas and hum on the incoming side. This never translates to hum in the speaker so it’s a mechanical hum. However if there’s a lot the transformers get saturated and heat can start to build up meaning the transformer cannot perform at its full capacity. So a DC Blocker of like any kind will reduce/remove this. There are lots of discussions in this forum related to it so search around a bit. The DC is caused my something with a motor on your grid or LEDs, Dimmers and such. Heat pump, dishwasher, washing machine, fridge, radiators etc

I used to have a constant, audible hum on my power supplies and power amps. Not too loud but definitely audible. They also used to buzz loudly for a few minutes several times a day. I got used to it. Then I had a dedicated mains feed installed and the constant hum fell pretty much silent. I still get the loud buzzing several times a day.

I turned off the other consumer units in the house meaning that only my hifi had an electric supply. The buzzing several times a day still occurred. I am told it is most likely DC on the mains from outside my house, and therefore beyond my control.

I tend not to fret about things I cannot control, and the dedicated mains made such an improvement to my system, that I am a happy boy.

If the hum is caused by an electrical device in your home, a dedicated mains circuit from a separate consumer unit may well help. (Even if it doesn’t, it’s a worthwhile thing to do.)
If the source of the hum is outside your own house, dedicated mains won’t improve it, although I would recommend doing it anyway if you can.

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Isol8 DC blocker sorted out my intermittent buzzing. A worthwhile investment to me.


The following may help you eliminate certain areas

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Mine cost me £110 delivered…does the job wonderfully.

Which one are you using please?

Absolutely correct Chris. We do need to be careful not to dress dedicated mains up as some sort of panacea. If you live in a residential street with lots of neighbours all putting demands on the mains supply then even with “dedicated” mains feeding your hifi transformers will still hum. Possibly not as much but they still will.

Stu…look at ATL Audio…


Don’t worry, although annoying. This almost certainly is caused by the toroidal transformer saturating due to asymmetric mains or so called DC on the mains, which is not the same as dirty mains… as the mains can be clean but asymmetric. Large toroidal transfers are relatively efficient and therefore are more liable to saturate.

This is likely caused by an asymmetric load in your house or neighbours on the same phase as you. Washing machine heaters, dishwasher heaters, laser printers, hairdryers can be culprits.
If really annoying you can try a commercial mains DC blocker… or if you have old wiring in your house you may benefit from a separate radial for your Hi-Fi, but if you have newish wiring that is unlikely to help.
There are also mains isolators which are large transformers which can help as well… but these can end up buzzing instead of your Hi-Fi…

I wonder — can high-ish voltage cause transformers to hum too?


Yes …as that brings the transformer nearer saturation anyway

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Thanks all, very informative. This morning I tried switching all other circuits off in the house but the buzzing remained. Only thing I didn’t do was unplug all the upstairs sockets on the same circuit as the power supply as I wouldn’t have been very popular! Will try that later though. I have a reef fish tank with LED lights and a number of pumps which I thought would be the culprit, but seemingly not.

Presumably the buzzing would cease pretty much straight away if the culprit was disconnected?

I’m not worried about the unit itself as the XPS it replaced did exactly the same.

House was built new ten years ago so wiring should be fine. If I can’t isolate it in the house I’ll try a DC blocker.

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I have a very similar experience. HiCap DR buzzes like mad all the time, XPSDR was totally silent, as is my recently acquired 555DR. All behind Isol8 axis blocker…

Funnily enough I was checking some devices for electrical noise a couple of days ago, using that highly sophisticated precision instrument, the portable AM radio.
I pointed it at an iPhone charger first, just to check it was working. When I turned the charger on, the noise started immediately. When I turned it off, though, the electrical noise continued unabated for about a minute.

There was probably a little residual charge in the unit till it ran down
The led on some units stays on for ages after they have been completely unplugged

I’m guessing you know all this though!!

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