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Greenwave EMI Meter Review

Rate this EMI Meter:

  • 1. Waste of money (piggy bank panther)

    Votes: 115 84.6%
  • 2. Not terrible (postman panther)

    Votes: 10 7.4%
  • 3. Fine (happy panther)

    Votes: 4 2.9%
  • 4. Great (golfing panther)

    Votes: 7 5.1%

  • Total voters
    136

amirm

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This is a review and detailed measurements of the Greenwave Broadband EMI Meter. It was kindly drop shipped to me by a member and costs US $135.
Greenwave Broadband EMI Meter Review.jpg

The device is simple: you plug in the AC cord (see on the bottom) into an AC outlet which both powers the unit and shows/sounds a couple of values and buzzes through the small speaker. They are quite popular at audio shows to demonstrate the before and after effect of power filters. The unit attempts to show both before and after levels in blue LED above but it is subject to failure as you see above. It seems to sample the noise level and if there is a change, it shows a new value. This works sometimes if you plug it in just right. Otherwise, the mere act of plugging in the unit causes it to read differing measurements, making it think a filter has been added to the circuit.

Company provides scant specification for the unit:
Greenwave Broadband EMI Meter Specification.png

But what is there should be an alarm to audio users as the lowest measured frequency is 3 kHz. And the highest 10 MHz. In other words, bulk of what it measures is above audible band.

I was originally hope to try to find its frequency response and linearity but sweeping an input tone through it. Alas, since it combines AC power with source of noise measurement, this was not easily feasible (I would have to build a high-voltage noise injection interface). So I resorted to just some spot checks as you see below.

Greenwave EMI Meter Measurements
As always, I start my measurements with the noise and spectrum of my "raw" AC mains power strip which has a number of devices plugged into it:
Raw AC Spectrum Measurements.png

We see that the bulk of the harmonic noise and distortion is under 1 kHz. Therefore measuring from 3 kHz as the Greenwave meter performs, is of little value. Still, I plugged the unit in, only to have it overflow (it shows 1---).

So I went the other extreme and tested it with my B&K 9801 Lab AC generator. This is its spectrum:
BK 9801 AC Spectrum Measurements.png


We see far cleaner output with second harmonic at -74 dB. Total noise+distortion has dropped from 2.5% to 0.05%. Here is what the meter shows now:

Greenwave Broadband EMI Meter Lab AC Generator.jpg


On one hand it is correctly showing lower value. On the other hand, the buzzing noise it made was much louder than when fed from my "dirty" Raw mains! I don't know what it is using to source that noise. I briefly "powered" the unit with my analyzer and the pitch increased with the input frequency. So it seems to be just be feeding AC into that speaker but then I don't know how it would make noise in response to ultrasonics. I would think that it would need to demodulate the input waveform. Regardless of what it does, I would ignore the noise. Alas, it is quite annoying so I wished it had an on off switch for that.

That's all I have for you.

Conclusions
Directionally, the testing shows that the meter in there is showing something proportion to level of input noise. How correct it is, is hard to say. The fact that company documents it to work from 3 kHz and up, should automatically disqualify it from usage for audio. I know some audiophiles think any radiation is bad but remember, your equipment internally performs massive filtering of such high frequencies. Yes, there are rare cases of AM radio leaking into circuit but unless that is what you are facing, do not confuse noise over AC line with noise level inside the power circuits of your audio gear!

I can't recommend the Greenwave Broadband EMI meter. I think it easily misleads people to spend money on power tweaks which have no value as far as improving your audio gear.

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As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

SuicideSquid

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I was curious if these devices were sold as audiophile tweaks so I looked the company up.

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.
 

Balle Clorin

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I bought this unit just for fun and to see how it reacts in different environment. It clearly reacts to dimmers , washing machine a such. It also registered much lower power noise after my apartment building got a new and larger electrical inlet . My mV values are down to 28mV so my system must sound just fantastic , right? !

It did nothing to improve my sound but was interesting in a kind of useless way.It did confirm that some “filters”( I borrowed and returned) do more than others to the mV readings, even if none of them improve the sound.
 
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AndreaT

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Basically a LW-MW radio band detector. I would not be surprised to find inside a tunable circuit and a frequency sweeper. It is not even broadband, as claimed.
 
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ing.daniele

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this EMI meter it is used by some youtubers to test the filtering of devices such as PS AUDIO P12 and QUTEST NIAGARA. it's easy like that, snake oil
 

KxDx

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I was curious if these devices were sold as audiophile tweaks so I looked the company up.

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.
It's the current in the power lines that I'm more concerned about.
 

sweetsounds

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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

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.
 
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fastfreddy666

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Ghost hunters use a similar device: An EMF meter. It comes in handy when your house is plagued by ghosts. It detects unexplained fluctuations in electromagnetic fields.
Well, not exactly. Electromagnetic Fields are composed of two different but related fields.. An electric field (E-field) and magnetic (B-Field) Electric fields are created by voltage and measured in volts per meter (v/m). An electric field will exist even when there is no current flowing. Magnetic fields are created when electric current flows: the greater the current, the stronger the magnetic field. Magnetic fields are measured in Gauss (G) and milliGauss (mG) or Tesla and microTesla (mT). 10 milliGauss equals 1 microTesla.

WHO DO YOU GONNA CALL? AUDIOSCIENCEREVIEW.

There is no scientifically proven link between the existence of ghosts and cold spots or magnetic fields. Bummer. People are unsufferable.
A former president of the USA who will not be named implied that the election was stolen from him in 2020. I quote. “In actuality, the Big Lie was the Election itself.”
WITCH HUNT. Storm the Capitol. Witches aren't real either. Others say that the ingredients in COVID-19 vaccines are dangerous. Well that's not true either.
And Don't get me started on those QANON <beep>

Why I am surrounded by conspiracy nuts theorists?

In audio there are also some nutjobs subjectivists who think they have "golden ears" and can hear anything that science cannot detect.

So I just stumbled on this article on tracking angle (1)

I quote: "Both the CD and SACD editions are also MQA encoded, which means if you transfer the CD files onto a computer and load it into Roon or Audirvana, when you stream it from your drive if your DAC does MQA it will unfold the original 384/24 bit DXD "master file". In other words you get the "master tape"! Not a copy of the master, not a third generation of the master, but the master.

And somewhat later in the same article

"If you're used to the vinyl edition and then hear the DXD version, you'll know from the opening bass line of Lee Hazelwood's "This Town" that this version is in another class. Barber's voice sounds "sweet" on the LP. She sounds eerily in your room on the master file. There's a serious uptick in overall transparency and macrodynamic detail and resolution.

MACRODYNAMIC DETAIL AND RESOLUTION ARE EVEN BETER THAN THE VINYL VERSION.

Throw your turntable in the garbage people. Because the compressed MQA version will magically turn into the master recording and will sound even better

And on the eight day God created MQA. <sarcasm> The author of the article must have an IQ we can only dream of. This is precisely how digital audio works. </sarcasm>

Oh and by the way. MQA should not be confused with DXD. DXD is a PCM signal with 24-bit resolution (CD is 16 bits) sampled at 352.8 kHz – That is six times the 44.1 Khz sample rate of a CD: 44.1 kHz, The format is used by audio recording studios for mastering.

This format is later converted to DSD to be used on a SACD. DSD64 is stored as delta-sigma modulated digital audio, which is a sequence of single-bit values at a sampling rate of 2.8224 MHz. This is a 6 times the samplerate of a CD. DSD256 uses a sample rate 256 times that of a CD. That is a staggering 22.5792 MHz. In addition there is also DOP aka Audio over PCM Frames which is used for embedding DSD into PCM audio streams. You can play DOP encoded DSD FLAC files on any DAC that supports it.

And we're back to PCM. This is the way.

DSD512 is a little over the top. You need a relatively fast PC and the files are huge.

2x44100 (stereo) x 256 / 8 = 2.844.400 bytes per second
So one minute will require 2.844,400 x 60 seconds / 1.048.576 (=1 MB) = 160 MB That is only 2.844.400 x 60 x 60 / 1.048.576 / 1024 = 9,5 gigabytes (GiB) per hour

I THINK WE NEED A BIGGER HARD DRIVE.

(1) https://trackingangle.com/music/how-best-to-hear-patricia-barber-s-clique
 
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Robbo99999

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I guess this device is just about as unnecessary as the Greenwave AC Filter that was reviewed yesterday, so that's my take on it!
 

DesertHawk

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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.
 

Nango

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So, a generally functioning device for... no one knows what exactly :D

Oh, silly me, for burning 135 $ of course.
If you paid 135€ for that and assuming that supposes a financial effort to you, believe me, you WILL notice better sound, no matter what ASR says. Even if they said it is garbage, you will hear better sound from now on.
 

respice finem

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If you paid 135€ for that and assuming that supposes a financial effort to you, believe me, you WILL notice better sound, no matter what ASR says. Even if they said it is garbage, you will hear better sound from now on.
That's how such "business models" work, for those gullible enough :)
 
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