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Post by MartinT on Mar 16, 2024 20:49:41 GMT
If the filters clean the incoming supply is there any "dirt" to be rejected? Just answering this bit, no filter is perfect. Ergo, you are never completely rid of mains noise. When that noise hits the power supply of your hi-fi component, it is subject to PSRR (Power Supply Rejection Ratio), which can never be 100%. So some noise ends up getting through. If the component is analogue, the effects may not be too great (big generalisation). If it's a DAC, the core of any digital system, the noise can still be ruinous. There is also the question of what frequency the noise is centred around. High GigaHertz noise can inflict more damage since it penetrates more easily (again, big generalisation). The prevalence of wi-fi, mobile data, DAB, TV and satellite broadcasts, gadgets and microwave ovens are not helpful and create a whole fog of airborne noise little of which was around in the 1970s. |
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Post by MikeMusic on Mar 16, 2024 20:51:57 GMT
Assumed mini fluorescents would be noisy which is why I swapped to LED
Not compared to incandescent
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Post by MartinT on Mar 16, 2024 20:53:16 GMT
Both CFCs and LEDs are bloody noisy, especially if dimmable.
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Post by MartinT on Sept 14, 2024 15:11:23 GMT
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Post by mattspl on Sept 15, 2024 12:01:18 GMT
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Post by MartinT on Sept 15, 2024 12:19:16 GMT
Not effective at gigahertz frequencies, according to their graph.
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Post by MartinT on Oct 5, 2024 12:06:06 GMT
There has been a change in the levels of noise on the house's mains power. Typically, the display was reading 50-70mV with nothing large running. Since yesterday, it is cycling about every 3s, from around 70mV to a very high level of almost 600mV.
I've been around the whole house and nothing we have is causing this, it's coming in from outside. The only change I can think of is the neighbour's twin superchargers for their two EVs. Is this a cyclic charging pattern for big batteries?
I've tried all my plug-in filters and none of them are helping, with most increasing the noise as already witnessed.
I've just had a very critical listen to the system and I don't think the noise is affecting sound quality - thank goodness for regenerators!
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Post by stellabagpuss on Oct 5, 2024 13:53:16 GMT
That's good news Martin, glad it's not effecting the sound.
That's the reality of our power supplies, we really never know what's in the street, effecting the power supply before it gets into our home.
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Post by MikeMusic on Oct 5, 2024 15:20:13 GMT
EV charging
Hmm.
Is that 3 phase they have ?
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Post by MartinT on Oct 5, 2024 15:44:45 GMT
Is that 3 phase they have ? Yes, for the many kilowatts of charging power. |
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Post by MikeMusic on Oct 5, 2024 16:03:22 GMT
Is that 3 phase they have ? Yes, for the many kilowatts of charging power. So far so good. When all the neighbours have them will it jump into your circuit, or something equally bad ? |
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Post by MartinT on Oct 5, 2024 16:24:26 GMT
Don't know yet. Need to check the noise levels when they are both out with their cars.
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Post by mattspl on Oct 5, 2024 17:31:21 GMT
Might be time for a dedicated Transformer Martin
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Post by MartinT on Oct 5, 2024 21:00:52 GMT
Might be time for a dedicated Transformer Martin What are the filtering characteristics of such a transformer? Will they kill high frequency noise? |
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Post by nicholas on Oct 5, 2024 22:32:21 GMT
Quality audio transformers may well manage high frequency noise better than the raw current that leaves an outlet. They work by transmitting signals through two or more coils of wire, known as windings, which are situated around a magnetic core. The difference between the input and output signals is called the impedance ratio.
General characteristics of transformers:
Impedance matching
Audio transformers can change the impedance value of a circuit, which is important for transferring maximum power and achieving good audio fidelity. If the impedance is mismatched, the sound will be distorted and weak.
Block DC current
Audio transformers can block direct current (DC) signals from passing to the output, while allowing alternating current (AC) to flow. This feature is useful for audio recording devices.
Electrical isolation
Audio transformers can electrically isolate one audio device from another.
Increase or decrease voltage
Audio transformers can increase or decrease the voltage of an audio signal.
Convert from unbalanced to balanced
Audio transformers can convert a circuit from unbalanced to balanced and vice versa.
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Post by MartinT on Oct 5, 2024 22:40:48 GMT
In this application, you're looking for a transformer where the secondary winding will respond to the power frequency (in my case, 50Hz) but will impede those frequencies where noise exists (kHz to MHz) so that it becomes a noise filter.
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Post by mattspl on Oct 6, 2024 18:16:45 GMT
Might be time for a dedicated Transformer Martin What are the filtering characteristics of such a transformer? Will they kill high frequency noise? I’m not sure about filtering as such, but it would isolate your mains supply. I’m not familiar with the workings of the PS Audio regenerators, but do you know if they contain an isolation transformer? If not, that could be something to look at. I’d speak to Tony about it, as I remember he suggested a few mains solutions to me some time ago, including a voltage regulator. |
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Post by MartinT on Oct 6, 2024 18:23:58 GMT
Thanks, Matt.
I'm holding all thoughts until I receive the second line noise detector.
The regenerators certainly have a lot of filtering but it's all part of the complex dynamic tracking amplifier that provides the regenerated power. I can't answer the question about isolation.
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Post by MartinT on Oct 14, 2024 13:52:27 GMT
I have just received my LHY NH-161 wideband powerline noise analyzer. I shall do some testing and report back.  |
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Post by MartinT on Oct 14, 2024 14:16:19 GMT
The new LHY is different from my original meter (also branded LHY) in that it does relative measurements rather than claim to provide an absolute noise level. That's fine with me as you will mostly want to know whether noise is higher or lower than another location or a different filter, for instance.
The process is to set the display to 100 as the baseline noise from a standard unfiltered socket. Then move it to other locations or outputs to see/hear the difference. The first thing I note is that this one is much more sensitive, even picking up some audio (sounded like radio) on my mains feed to the music room.
I haven't tested against plug-in filters yet, but the first thing I tried was checking the output of my P3 regenerator. That gave a reading of 33, so the P3 is reducing noise to one third of the raw power. It also has no trace of audio on the output. Good start.
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