Quick point re warranties. If you bought a new unit from your dealer, the warranty starts on the day you bought it, not the date of manufacture.
(Demo unit warranties start on day of dealer purchase.)
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https://www.soundonsound.com/techniques/identifying-solving-mains-supply-problems
This is an interesting article by Ben Duncan, aimed at studios really but pertinent to the discussion I feel.
I have several humming transformers, Naim and others, which I havenāt been able to cure as yet.
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Has anyone got a diagram of what the 50hz sinusoidal AC waveform looks like with " dc offset" ? There have been a few explanations which appear different.
For me dc on an ac waveform is a period of time for which the ac is well, not alternating. Iām seeing it as a " flat spot". But again, I donāt think that is what we are describing. And perhaps dc offset may be the wrong phrase.
No. DC offset is not DC current on an AC line. It is a deformation away from the zero point on any AC sinewave. Normally this is associated with problems on an analogue audio signal caused by dodgy mics or phono stages.
Here we just mean the same thing applied to a 50/60Hz mains wave. So if you have an offset of +3v (for example) on a 230v supply the wave goes 233v in one cycle and 227 on the other. Thatās your offset.
You can measure it with a multimeter in DC mode though. But what you canāt do is see the effect on the sinewave.
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Got it. Thanks. So the zero point. For want of a better word, it offset. So the two halves will have different peek voltages.
Is this imbalance what we are hearing then?
So this imbalance between half of the waveform are created by certain nasty items that are using half wave rectification?
Youād need someone with a background in electrical engineering to answer that. What mechanism in offset or over voltage leads to movement and thereform hum is beyond my meagre grasp.
Luckily the forum has just such people.
perhaps that someone could also invent a plugin device that measures DC offset - theyād make a killing on this Forum (ok, fair enough not a massive audience perhaps)
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Its not really DC, its a asymmetrical distortion of the sinusoidal wave form.
Its called DC because it behaves as DC in a coil such as a transformer with a high current inrush in the distorted section.
Basically its one half of the sinusoidal wave being greater/less than the other.
Typical & well understood cause is a half wave rectifier on the supply such as used for speed & heat control with hair dryers & electric blankets. The half wave load reduces amplitude of half the wave & leaves the other half cycle untouched.
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Thanks. That was where my head got to. Nasty half wave rectifying things on my system.
Are we talking about a combination of factors though.
- The ānormalā low level hum associated with Naim toroidal transformers.
- The introduction of other devices causing the anomaly known as dc offset.
- The eventual failure/compacting of the transformer mountings.
Establish the main cause and treat accordingly.
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I donāt think itās normal. I think misery loves company and common problems flock to the forum. Iāve yet to actually hear any Naim transformer that is anything but silent in every place theyāve been plugged in.
None of mine could be described. Especially the 1.2kva ones ( yep, there are 2 of them) in my power amp.
At the first hint of asymmetrical offset the cd5xs is off, followed by the xpsdr. HC then follows. The napsc with the 282 Iām trialling is silent at all times.
Youāve been very fortunate then.
Iāve had two silent Naim transformers in ND5XS and XP5XS, and currently have two humming transformers in XPS2 and 555DR.
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The *XS transformers are small so may hum at a higher frequency with very low energy.
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I suspect its your voltage. I understand your area of Japan is 100v 50Hz & your equipment is wired for USA 120v 60Hz, so your voltage is at the lower end of the transformer specā¦
Iām wary of making assumptions, but I suspect the UK Naim users with up to 250v are more troubled than are the mainland Europe Naim users with 220v
ā¦and the āonlyā thing it effects is a Naim system, which is why there is a thread here discussing it.
Donāt you believe itā
I have a burglar alarm system with a noisy transformer located in a small lower floor cupboard type room that could be heard in my bedroom. The company refused to consider changing it so as soon as the warranty was over I changed it.
A buddy installed a balanced power supply for his audio & AV systems, problem was it was in the room & it was an 'orrible noise. He ended up having it installed next to the CU & meters in the garage.
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I had a air conditioning system keep me awake once ābuzzing all night longā, no matter what i did it buzzed, it just kept on buzzing. What i did? Yank the wires out of the wall and threw the thing into a skip. Problem solved.
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Not sure Iām gonna skip āxā thousand of naim kit to get rid of a hum.
Paul at PS Audio talked about the negative effect of DC and humming transformers recently. He said it will create imbalance on the transformer which is why an On Off cycle many times make the system sound better since you set the transformer balance to default again.
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