Greenwave EMI Meter Review

[Badunn]

I have a thick sweat top that definately improves the sound quality of my system when I wearing it. Absorbency properties to die for. Friends and relatives agree with me. 30 tog too! Saves on heating bills. Double benefits!!
Amir… your address please… test It quickly and publish as goes on sale soon. Need the plaudits.
Ps - don’t worry about returning it… I‘m knitting more prototypes

 

[Hart]

If you have black speaker grills you should not need this product, however if you have white grills you may notice some buildup after time.

 

[Audioagnostic]

Is the B&K 9801 Lab AC generator marketed as the ultimate audiophile power supply?

Much cleaner than ordinary AC. Must have a devastating effect on the soundstage. No?

 

[audiotron]

Based purely on hopium.

 

[Prana Ferox]

A question from someone who isn't an electricial engineer. So, this is just my understanding so I could be off, but when Amir tests equipment such as a DAC, he is feeding it a current that corresponds to a 1 kHz tone which looks like a sine wave and then you can take the FFT to show any imperfections in the sine wave*. But in this review (and the last) we are looking at a sine wave of the electrical current itself. Which, I think, if it were clean would be a perfect 60 hz. These devices are supposed to "clean" any imperfections (and there's a whole slew of reasons why that doesn't seem useful or practical, the largest being the AC/DC conversion). But where I get confused is when Amir talks about the distortion in the electrical current being inaudible because the bulk of it is north of 20 kHz which isn't audible. Is there a 1 to 1 translation between electrical current wavelengths and audio signal wavelengths?

Does this question even make sense?

*actually an fft is just a rebasing of the axis. You could show imperfections by overlaying a "perfect" 1 kHz sine wave but it would be much more difficult to see where it is "off" than by looking at the fft.

The nature of noise and how it can be 'reflected and refracted' in an AC circuit means it generates distortion at integer multiple frequencies of itself, so low frequency noise generates higher order, i.e. higher frequency harmonics. 60hz noise makes 120hz noise, 180hz noise, 240hz noise etc. It doesn't really work the other way. That is extremely oversimplified but it's much better explained visually. So RF noise can't generate audible-band distortion.

Also as repeated in pretty much all of these power supply reviews, a basic basic basic amplifier power supply's task is slamming the AC power signal to DC, and that filtering arguably gets more effective against higher frequencies. (RF noise can make your amp oscillate but that's a different problem and also actively designed against.)

I wonder what this thing would do with a broadcasting cell phone nearby. They drive my radios nuts even when the radios aren't on.

 

[DesertHawk]

The nature of noise and how it can be 'reflected and refracted' in an AC circuit means it generates distortion at integer multiple frequencies of itself, so low frequency noise generates higher order, i.e. higher frequency harmonics. 60hz noise makes 120hz noise, 180hz noise, 240hz noise etc. It doesn't really work the other way. That is extremely oversimplified but it's much better explained visually. So RF noise can't generate audible-band distortion.

Also as repeated in pretty much all of these power supply reviews, a basic basic basic amplifier power supply's task is slamming the AC power signal to DC, and that filtering arguably gets more effective against higher frequencies. (RF noise can make your amp oscillate but that's a different problem and also actively designed against.)

I wonder what this thing would do with a broadcasting cell phone nearby. They drive my radios nuts even when the radios aren't on.

Thank you so much for a reply. This is helpful.

 

[Zapper]

in defense of the unit, it says to measure EMI on power lines. Actually, EMI is a valid concern in power electronics, in PFC as well as EMC.
Badly designed dimmers, LED, motors etc. inject noise, and there are necessary regulations to it.

And it is not about audability, it is about RF frequencies.

So the device should be tested as an EMI meter like here

https://www.edn.com/review-tool-measures-power-line-emi/

i do agree that any properly designed electronic device should be conform and immune to low levels of EMI. But I can hear injection of noise from fridges and vacuum cleaners into audio.
An EMI filter is a good idea to get rid of buzzing noises If you have them.


As for health: many people are concerned of long-term health impacts of low-level electromagnetic fields. While the WHO classified them as pot. cancerogenic in 2011, there is little scientific evidence today. https://en.wikipedia.org/wiki/Electromagnetic_radiation_and_health

I own an EMF meter and AC lines emit a small amount of radiation (in line with what wikipedia says around 10V/m in my home), so it's very low and only measurable around the outlet. Don't think that this device measures EMF in the air as well. However, some cheap Chinese power supplies could be found as noise sources.

I agree. Amir is mistaken that only audio frequencies matter.

RF frequencies can be hard to filter. They can spread inside electronic chassis by conduction and radiation through multiple paths. Capacitors look like inductors at high frequencies, and inductors and transformers can look like capacitors. The semiconductor junctions in solid state electronics can rectify RF EMI into DC and lower frequency components. These rectified EMI voltages can cause functional disturbances, and even IC failure in extreme levels.

Electromagnetic immunity and emissions testing is required for ICs and electronic assemblies in certain industries, including automotive, medical, military and aerospace. Probably few audio components are tested for electromagnetic immunity, and some could potentially be sensitive to it through unwitting mistakes in the circuit design or PC board layout.

That said, I think that EMI interference with domestic audio products is a rare occurrence.

 

[ing.daniele]

However, some cheap Chinese power supplies could be found as noise sources.

like power plant p12 . Not chinese but same

 

[CedarX]

It's worse than that - they're sold as HEALTH devices. This company is trying to convince you that noise in your power lines is bad for your health.

Absolute scumbags.

They are not wrong: some audiophiles may experience seizures when finding about noise in power lines… and spending thousands in power line filters is certainly suicidal behavior.

 

[amirm]

RF frequencies can be hard to filter. They can spread inside electronic chassis by conduction and radiation through multiple paths. Capacitors look like inductors at high frequencies, and inductors and transformers can look like capacitors. The semiconductor junctions in solid state electronics can rectify RF EMI into DC and lower frequency components. These rectified EMI voltages can cause functional disturbances, and even IC failure in extreme levels.

This device only measures what is conducted over AC line so your point is off topic with respect to this review. Even outside that, the metal boxes of audio gear provides strong immunity against RF incursion unless it is insanely strong. Even if this incursion occurred your speakers can't play them anyway so there is a stop there. To the extent they get demodulated into AM, then sure, if you are hearing such noise, you want to investigate the source. I have only heard of this with long wires and closeness to powerful radio stations.

If this kind of RF incursion was a problem people would have already gone crazy with many sources courtesy of their phones, Wifi and unregulated 2.5 Ghz. Yet they are not.

People use these devices not because they have a problem, but because they don't and think fidelity improves. For fidelity to improve there must be interreference in audio band and that precisely what I test.

 

[wwenze]

Add: Same fish logo was found inside audiophile ethernet switch, so I guess we can safely say that this is also an "audiophile" product

 

[PeteL]

But have you actually listend to it?

listened to what? Sorry it’s not fully clear what “it” stands for in the context of this review.

 

[MacCali]

Is the PA7/PA7+ review coming soon o.o

 

[milosz]

High levels of RF radiation can indeed be bad for audio gear - it can cause noise in the audio no matter how good the audio gear's power supply filtering is. But there has to be really VERY high levels of RF for this to happen. For example, me living in a highrise 1800 feet from the 500 KW transmitters atop the Sears tower... the kind of situation where you can touch an oscilloscope probe to any metal surface and measure a small RF voltage there. I've measured as much as 70 mV at 89.7 MHz in one such situation on a soup spoon. VHF and UHF RFI is VERY HARD to exclude from audio gear if the field intensity is high enough.... this happens in near proximity to transmitters.

But it's not the power line that is at fault. The power line of an audio component is one route that environmental RFI can enter a device, but it will also get in and irritate battery-operated gear. And the power line is not going to carry these VHF/UHF signals down the road to more distant locations, it just doesn't happen.

And this gizmo isn't going to help you track down this kind of EMI. In fact, I'll bet you that if used close to a powerful radio source, this thing would go crazy.

 

[roog]

It would be interesting to know how it works or not, because based on my admittedly fairly limited experience of witnessing EMI tests, it requires a controlled environment, accurate set up and sophisticated/costly instrumentation.

135 Euros you say,....hummm?

 

[fpitas]

If you have black speaker grills you should not need this product, however if you have white grills you may notice some buildup after time.

I use carbon-filled EMI foam to scrub away EMI buildup.

 

[FrankW]

listened to what? Sorry it’s not fully clear what “it” stands for in the context of this review.

"It" stands for sarcasm

 

[fpitas]

Golfing Panther from me .... this is an excellent Ghostbuster tool

If it keeps you from crossing the streams, it's worth every penny!

 

[wwenze]

Well considering this is what you can get for $30 I'd expect at least FFT capability for $135

And of course it goes down to 20Hz which is necessary because often the reason for buying these is to find out if there is any damaged AC cabling inside walls.

Fact titbit: Airborne radiation occurs biggest when the cable encounters a huge impedance difference. A broken cable would hence emit more radiation at the break point, and so will wall sockets.

 

[fpitas]

Well considering this is what you can get for $30 I'd expect at least FFT capability for $135

And of course it goes down to 20Hz which is necessary because often the reason for buying these is to find out if there is any damaged AC cabling inside walls.

Fact titbit: Airborne radiation occurs biggest when it encounters a huge impedance difference. A broken cable would hence emit more radiation at the break point, and so will wall sockets.

All the more reason to wear my foil hat, even in my own house.