This is a review and detailed measurements of the Greenwave 2500i AC line filter. It was kindly purchased by a member and drop shipped to me. It costs US $35 each.
Can't say it is the prettiest thing in the world but I guess you can plug it into AC where it is not seen. Using it with my power strip was a pain as it is large and wants to sit horizontal, blocking many outlets. FYI company recommends buying many of these (5 or so for kitchen and such???). They also highly recommend buying their EMI meter to see the results ($139 -- separate review to come).
Company doesn't make any direct claims about audio improvements but actually goes way beyond that with health claims:
I can't test those claims but sure can see what it does do. So let's measure it.
Greenwave 2500i AC Filter Measurements
Per my standard protocol, I measured the spectrum of noise and distortion in my current AC feed (which powers my entire workstation) using a 100:1 differential probe:
We see 2.5% distortion comprised of harmonics of 60 Hz. Let's plug in the Greenwave 2500i and see what happens:
Overall distortion+noise does not change and remains at 2.5%. However, there is some reduction of the minor distortion spikes at higher frequencies. Let's examine that with much wider bandwidth going 1000 kHz:
We see the classic performance in all of these AC filters: they only start to do something starting from a few kHz and go up from there. Yet, our "problem" with AC is in much lower frequencies and hence the reason overall distortion did not change with the filter.
Plugging in the company's EMI meter shows a 98% reduction in noise. Specs for that device says it starts to measure at 3 kHz and goes up to 1 MHz so no wonder it shows that kind of result. It matches the effectiveness of this filter, not want we are interested in measuring.
As regular readers know, we don't care about how clean the AC is as the power supply in any well engineered audio device already has this filtering and then some. And we only listen to the output of audio device, not AC mains. So let's measure that using Topping A90 preamp, starting with just raw AC:
To give the benefit of doubt. I have expanded the dashboard measurement to 90 kHz (instead of normal 22.4 kHz which is the audible band). Using this wider spectrum, we see a very tiny spike at -140 dB (25 dB below threshold of hearing). That spike is where there was in the raw AC spectrum at -55 dB. The A90 design has reduced this by 85 dB.
Now let's plug in the 2500i:
We see that the spike is gone. The AC FFT showed that the spike was filtered by the 2500i so combined, we managed to bury it into the noise floor. Of course the spike was ultrasonic so wasn't audible at any level and what was there at -140 dB doubly made it so. But hey, we can show that we can precisely measure the effect of such devices well below our hearing threshold. So it is not that we can't measure them. It is that we can measure them and what they do has no impact in audible band (Topping filtering is much stronger there).
FYI, I measured the power consumption of the 2500i and my power meter shows 0.1 watt. Not much but if you plug in multiple, it could add up to a tiny bit.
Conclusions
The Greenwave 2500i is yet another AC filter which only works at higher frequencies, with most effectiveness in ultrasonics. Our audio devices are already providing superb filtering of AC noise and distortion just as well. For this reason, there is no hope of improved performance as a result of plugging in one of these filters.
Needless to say, I can't recommend the Greenwave 2500i for audio applications. Whether it does something for your health, I leave that to your common sense.
------------
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/
Can't say it is the prettiest thing in the world but I guess you can plug it into AC where it is not seen. Using it with my power strip was a pain as it is large and wants to sit horizontal, blocking many outlets. FYI company recommends buying many of these (5 or so for kitchen and such???). They also highly recommend buying their EMI meter to see the results ($139 -- separate review to come).
Company doesn't make any direct claims about audio improvements but actually goes way beyond that with health claims:
I can't test those claims but sure can see what it does do. So let's measure it.
Greenwave 2500i AC Filter Measurements
Per my standard protocol, I measured the spectrum of noise and distortion in my current AC feed (which powers my entire workstation) using a 100:1 differential probe:
We see 2.5% distortion comprised of harmonics of 60 Hz. Let's plug in the Greenwave 2500i and see what happens:
Overall distortion+noise does not change and remains at 2.5%. However, there is some reduction of the minor distortion spikes at higher frequencies. Let's examine that with much wider bandwidth going 1000 kHz:
We see the classic performance in all of these AC filters: they only start to do something starting from a few kHz and go up from there. Yet, our "problem" with AC is in much lower frequencies and hence the reason overall distortion did not change with the filter.
Plugging in the company's EMI meter shows a 98% reduction in noise. Specs for that device says it starts to measure at 3 kHz and goes up to 1 MHz so no wonder it shows that kind of result. It matches the effectiveness of this filter, not want we are interested in measuring.
As regular readers know, we don't care about how clean the AC is as the power supply in any well engineered audio device already has this filtering and then some. And we only listen to the output of audio device, not AC mains. So let's measure that using Topping A90 preamp, starting with just raw AC:
To give the benefit of doubt. I have expanded the dashboard measurement to 90 kHz (instead of normal 22.4 kHz which is the audible band). Using this wider spectrum, we see a very tiny spike at -140 dB (25 dB below threshold of hearing). That spike is where there was in the raw AC spectrum at -55 dB. The A90 design has reduced this by 85 dB.
Now let's plug in the 2500i:
We see that the spike is gone. The AC FFT showed that the spike was filtered by the 2500i so combined, we managed to bury it into the noise floor. Of course the spike was ultrasonic so wasn't audible at any level and what was there at -140 dB doubly made it so. But hey, we can show that we can precisely measure the effect of such devices well below our hearing threshold. So it is not that we can't measure them. It is that we can measure them and what they do has no impact in audible band (Topping filtering is much stronger there).
FYI, I measured the power consumption of the 2500i and my power meter shows 0.1 watt. Not much but if you plug in multiple, it could add up to a tiny bit.
Conclusions
The Greenwave 2500i is yet another AC filter which only works at higher frequencies, with most effectiveness in ultrasonics. Our audio devices are already providing superb filtering of AC noise and distortion just as well. For this reason, there is no hope of improved performance as a result of plugging in one of these filters.
Needless to say, I can't recommend the Greenwave 2500i for audio applications. Whether it does something for your health, I leave that to your common sense.
------------
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/
