This is a review and detailed measurements of the PS Audio Noise Harvester and AC Cleaner. It is on kind loan from a member and sells for $99.
The harvester is a bit bigger and uglier than typical phone charger:
View attachment 69147
Claim to fame is that AC noise is captured gradually and then discharged all of a sudden into the LED on the right to get rid of it:
View attachment 69148
One wonders why a sudden discharge wouldn't be bad for your sound versus a gradual/constant thing!
As to discharging "all the unwanted noise" company shows no specifications or measurements to demonstrate that. It is trivial to measure noise so not do that?
Also, I see no indication of safety regulation on the device and on the website. It is one thing to lack such marks for low voltage devices but an entirely different matter when you plug something in to mains and leave it there. A safety flaws could lead to fire or worse. What would this thing do for example if a powerful external surge arrives? Does it open up gracefully or short and cause smoke?
Does It Do Anything?
A lot of tweaks sold to audiophiles make claims that follow the laws of another universe so we can't use our tools in this universe to test them. Here though, we can. AC mains is at 50 or 60 Hz. A filter better not touch these frequencies or you would loose the very energy you need for our device to function! As a result, filtering will be at some higher frequency, often well above hearing range making them useless for improving audio.
To determine the filter range, I set my Audio Precision to produce 21 volts output and captured and plotted that using very wideband response (1 MHz). I then inserted the Harvester in the middle to see the effect:
View attachment 69149
Hey! There is some good news here. There is filtering that occurs in the audio band and indeed, we have reduction of frequencies above 500 Hz with best response (naturally) at higher frequencies. There is a resonance causing that peaking but otherwise, we have about 20 dB of reduction. The harvester was blinking away happily saying it was doing its job.
Would this do us some good? Well, let's look at the spectrum of AC in the power strip that I use to power my analyzer, the PC and anything I review. To not kill myself or the analyzer, I used a simple AC transformer to bring the voltage down. Otherwise everything is the same:
View attachment 69150
In blue is the spectrum of the AC mains. Instead of the ideal single 60 Hz tone, we have a myriad of other tones. Highest peak is nearly -30 dB. This result in a THD+N of nearly 3%.
Once I plug in the Harvester, we get the graph in red. Yes, it almost looks identical because as I showed before, it doesn't do anything below 500 Hz. Unfortunately that spectrum between 60 and 500 Hz has most of our distortion and noise. What is above that has far lower amplitude.
Even in high frequencies we don't get much attenuation because the amount of energy harvested and dissipated by this box is too little. Imagine what it takes to power an LED for a fraction of a second. It is probably in microamps which would mean nothing in grand scheme of things. No wonder then that THD+N doesn't change (the number varies fair bit so don't focus on decimal places).
In addition to frequency domain, we can also look at the waveform in "time domain:"
View attachment 69155
We can easily see the effects of 3% distortion in how the tops of the sine wave are distorted (flattened mostly). Sadly, the Harvester does nothing to turn our ugly sine waves into pretty ones. With or without, the shape is the same.
At this point we have fully characterized the device. It is a low pass filter with very negligible effectiveness. But maybe it performs some magic that escapes these measurements but shows up in audio devices so let's test them with and without the Harvester.
AC Cleaner Effect on Audio Performance
Let's start with the most sensitive and highest performance "audio" device I have which is my Audio Precision APx555 analyzer. I put it in the loopback mode and measured its own distortion+noise over time. After a bit of time, I plugged in the Harvester and then took it out. This is the results:
View attachment 69151
As you see, it made no difference whatsoever even though we are measuring distortion and noise that is whopping -123.5 dB below full level! Why doesn't it care? Because it designed with the assumption that AC mains is never clean or remotely so. All the necessary filtering is performed internally which is a lot easier when dealing with low voltage DC, than high voltage mains AC.
OK, so that is a $28,000 analyzer so let's step down to a much more reasonable $500
Topping A90 which I recently reviewed:
View attachment 69152
The harvester blinking away saying it is doing something. But again, in super sensitive measurements representing far lower threshold than our hearing, there is no effect on noise+distortion at all.
Let's go even cheaper to $99
JDS Labs Atom DAC:
View attachment 69153
We can see how sensitive our measurement system is in detecting very small variations in performance of Atom DAC. Clearly there is some "noise" there to clean up but the Harvester does nothing for us.
Maybe we shouldn't use high-performance audio devices. For that, let's use the Schiit Modi 2 Uber DAC:
View attachment 69154
Not... one... thing... different! Surely the Harvester should have gotten lucky by now and did something. But it did not.
Listening Tests
Folks always come back and say "but I hear a difference, you should use your ears." So that is what I did. On the same computer used for above, I use an
RME ADI-2 DAC V2. Into that I use an Ether CX headphone. I plugged in and unplugged the Harvester multiple times but could not detect any difference whatsoever.
If you are hearing a difference, turn away from your power strip, have a loved one plug the device in and out at random times and have you raise your hand when you think it is plugged in. After just a minute or two, you will get the right answer which is there is no audible difference. Your brain concludes that there is less noise because you are told there is less noise with this device and hence you "hear it." Lack of change in audio waveform reaching your ears be damned.
Conclusions
In some sense it is a relief to find an audio tweak that we can analyzer and characterize what it does. It indeed filters "some noise." That filter is too small to begin with. But importantly is of no use because your good audio devices already filter that noise. Imagine how bad my audio system would sound if the 3% harmonic distortion and noise was let through! Which designer you cherish would sell you an audio device that doesn't do such filtering when it is so easy and cheap to do???
Remember, the company could easily measure noise and show the improvement with their own or other companies' products. But they have not. You wouldn't take a drug with no verification of its efficacy. Why would you trust a company to sell you something to "clean your AC" where no such evidence is not at all?
On top of that, you have a mains operated device which no third-party verification that is safe to be plugged in. As such, it is illegal to sell in probably every western countries if not others.
Be a smart audiophile. Don't put your guard down just because there are positive testimonials for such devices. I don't care how useless an audio device is. Some people will say it performs miracle. These people don't know how to perform a simple, bias controlled test to verify the truth. Don't listen to them. Don't put your guard down.
And before you say everyone who owns one likes it, watch this:
-----------
As always, questions, comments, recommendations, etc. are welcome.
June is turning out to be an expensive month. I will probably be close to shipping back 500 pounds of gear and have spent nearly $1,500 on gear. I can afford it but will feel entirely more positive if you all
donate it! https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
