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PS Audio PowerPlant 12 Review (AC Regenerator)

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amirm

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This is a review and detailed measurements of the PS Audio PowerPlant 12 (P12) AC regenerator. It is on kind loan from a member and costs US $5,499.
PS Audio PowerPlant 12 P12 Review AC noise and distortion regenerator.jpg

PS Audio nails the industrial design of the unit. I really like the casework as well as the look of the various graphical meters as you see above. There is even network/Ethernet support to monitor them over time and remotely:
PS Audio PowerPlant 12 P12 Review back panel ethernet AC noise and distortion regenerator.jpg

This is one heavy unit though despite its svelte height. Here is a shot from underneath:

PS Audio PowerPlant 12 P12 Review Bottom Fan ethernet AC noise and distortion regenerator.jpg


Looks like we have a toroidal transformer on bottom right and power supply circuit to its left. Then on top is the AC regenerator which is basically a high voltage mono amplifier fed by a specific frequency (60 Hz in my instance). There are large heatsinks on the amplifier cooled by those two fans. I don't know if it sucks air from bottom or what. If it is, the feet are too shallow to allow good airflow. You better not put this on top of anything else that generates heat for the same reason.

After I took the above picture with the P12 on its side, I went to rotate it down and something really sharp poked and tore up my finger. Put it back up and noticed that there are two sharp points in the sheet metal (one indicated with the arrow). Not only is this dangerous from handling point of view but also is poor design as they can catch and bend in or out. The two sharp points should have been wider and connected to each other (vertically). The tip of my finger is hurting a bit still as I type this. :(

In case you are not familiar with this class of device, they take AC input, convert it to DC. That DC is then used to drive a power amplifier that is driven by mains frequency. Idea is that they can generate AC with lower distortion+noise than what the power company provides you. One wonders what cleans its own power supply if one needs a clean AC to drive audio equipment but we digress. :)

EDIT: later investigation shows that the P12 may be a partial regenerator. It is take some of the AC input and generating the test. This would explain why it doesn't perform that way as a regenerator.

Company advertising makes lofty claims that are sadly not backed by any measurements:
PS Audio PowerPlant 12 P12 Advertising AC regnerator.png



"Sine-wave-perfect?" Nothing perfect exists in real life so that for sure is a stretch. How much we will see in measurements.

As usual there is also the claim of lower noise:
PS Audio PowerPlant 12 P12 Advertising Lower Noise AC regnerator.png


Again, if we can "expect lower background noise," why not show it to us in a measurement?

Being a high powered unit (think 800 watt amplifier), I worry about longevity and was reasonably happy to see a 3 year warranty. But then it had these exclusions:
PS Audio PowerPlant 12 P12 Warranty AC regnerator.png


Preventative maintenance? What would that be? Can't imagine they are asking the customer to open a unit lethal high voltages in it to clean those fans or circuits. The bigger issue is "connection to an improper voltage supply." Come again? I thought the purpose of this unit is to take improper AC supply and clean it up. And how would the customer know what is improper anyway?

Anyway, being an expensive product of its kind, the following testing is also a lot more expensive. To understand the flow, this is what we have here:

Raw AC Mains. This is what is powering my desktop computer, Audio Precision APx555 analyzer and any audio device I usually test. I measure this so we know what we are working with.

PS Audio P12 Output. The P12 takes raw AC and converts it to DC. It them modulates it with a sine wave with output regulated/nominal 120 volt. I measure this output and compare its quality to raw AC and my lab AC regenerator (BK Precision 9801).

Audio Power Supply Output. Almost every audio device also converts the incoming AC to DC. So I took both a switching and linear power supply and measure the DC spectrum of noise and distortion powered by either raw AC or PS Audio. If the theory of these products is correct, then the DC output of the power supply should be cleaner.

Analog Output of Headphone Amplifier. I tested a Topping A90 high performance headphone amplifier with both raw AC and PS Audio P12. Unlike the above tests, this is an actual test of fidelity and ultimately all that matters. The rest of the measurements help us understand what we are seeing here but ultimately they don't matter. Testing is performed both at one frequency and full suite of frequencies.

Let's get started.

AC Measurements
This is tricky business as we are talking 120 RMS volts (peak about 170 volts). This would damage the input stage of many measurement devices. Fortunately I have a differential AC probe (helps with not picking up stray signals/noise) that also has a 100:1 divider. This brings the voltage way down allowing me to use my Audio Precision analyzer with its full resolution to analyze AC power. This gives us far, far more accurate results than any AC line analyzer. First, we need to make sure the differential probe is not limiting the measurements so let's test it:

Differential Probe Distortion Measurements.png


26 volt is output by Audio Precision APx555 and then looped through the differential probe. As you see, the voltage is divided down to 0.26 volt (100:1). The probe is creating just a second harmonic that is at -95 dB. Add some noise to it and our SINAD drops to 81 dB. For audio equipment that is not great but for measuring AC it is extremely good as what we are testing has far more noise and distortion as you shortly see.

So now let's measure the Raw AC in my lab:

AC Mains Distortion and Noise Audio.png


Our AC waveform is distorted (tops of sine wave are rounded a bit) and noise added. If you look on top right, you can see what we have. The first tall spike is at 60 Hz which is the wanted frequency. But we also get a spray of harmonics at its multiples. We could treat this as a normal audio signal and compute its THD+N as show which is about 2%. P15 provides its own measurement but it underestimates it by a bit:
PS Audio PowerPlant 12 P12 Display AC noise and distortion regenerator.jpg


Maybe it is ignoring noise and just showing THD.

Now let's fee the Raw AC to PowerPlant P12 and measure what comes out of it:

PS Audio PowerPlant 12 P12 Measurements AC noise and distortion regenerator.png


We see a sharp reduction in harmonic spray with P12 resulting in our SINAD climbing from 36 dB (raw AC) to 67 dB (output of P12). We get a true THD+N of 0.46 which is much higher than 0.1 shown by P12 (0.1%). Fortunately we are still within the spec for P12 as I have copied and pasted in the center of the graph (< 0.5%).

I did notice raised noise floor though relative to our AC mains which surprised me. So I drilled down:

PS Audio PowerPlant 12 P12 Measurements FFT compared to mains AC noise and distortion regenera...png


RAW AC is in blue, and once passed through PS Audio P12, in red. We see that the red has lower harmonics but has much higher noise floor across the full spectrum of audio.

Let's compare the same to my BK Precision 9801 lab AC generator (about US $2,600):

BK Precision 9801 Measurements AC noise and distortion regenerator.png


Notice how SINAD has shot way up to 65 dB now, courtesy of much lower harmonic distortion and noise. We can compare them again using the spectrum analyzer:

PS Audio PowerPlant 12 P12 Measurements compared to BK Precision 9801 Lab AC noise and distort...png


So as an AC generator, the P12 is quite a poor one. Granted, my 98091 is rated at 300 volt-amp and the P12 is 1000 so maybe we allow some difference in distortion but not this much.

The unit as shipped and tested by me comes in "high regulation" mode. It keeps the voltage constant at the expense of distortion. So I thought I change the mode and compare:

PS Audio PowerPlant 12 P12 Measurements High current versus zone A AC noise and distortion reg...png


I am not seeing a difference. Maybe under heavy load it acts differently.

While on topic of not making a difference, there is a multiwave setting that goes from 1 to N. I changed that from 1 to 6 but it made no difference whatsoever in the output. I thought multiwave was for unit to generate different waveform than single 60 Hz. I like the company to show and document the waveform difference as you change this setting.

There is always an argument around these devices that they clean up noise above audible band. So let's test for that with 1000 kHz or 50X our audible band and see what is going on:

PS Audio PowerPlant 12 P12 Measurements wideband FFT compared to BK Precision 9801 Lab AC nois...png


We see that the results are the same and not much is going on above 100 kHz anyway. The lab generator remains cleanest with P12 having higher noise floor at lower frequencies but lower distortions than AC mains.

Audio Power Supply Noise and Distortion Measurements
Let's start with the output of a small switching power supply that powers a Topping DX3 Pro which I had handy. Here is its spectrum when fed by my normal AC mains:

Topping DX3 Pro Power Supply Noise and Distortion Measurement.png


I have heavily zoomed the vertical scale so that we can see what is going on. At normal scale it would look like a flat line that DC would. We see the worst case of noise is a spike between 1 and 2 kHz. Its amplitude is at -65 dB which may be objectionable. But remember, this is the raw DC going into the Topping DX3 Pro. Secondary voltage regulators and filtering is used to clean this up before use. But let's go with it and compare it to when we power the power supply through P12:

Topping DX3 Pro Power Supply Noise and Distortion Measurement vs PowerPlant P12.png


I say no difference but the output of P12 seems a bit worse with our spike now rising a few dBs. That nit aside, none of the "nasties" have been removed. Reason is simple: bulk of them are generated in the power supply. The incoming raw AC was converted to DC inside this power supply and filtered. So what the P12 cleaned up was not material.

Another class of audio power supply is linear. For that, I grabbed the external DC power supply that came from my GRAS headphone measurement system. Here is its output when fed from raw AC (blue), PS Audio P12 (red) and BK Precision 9801 lab AC (blue):

GRAS DC Power Supply Noise and Distortion Measurement vs PowerPlant P12.png


The process of getting DC from AC involves first flipping the negative cycle of the AC sine wave to positive. This doubles the frequency of the mains input and shows up as a result as 120 Hz spike. We see that there is no difference between the three methods of input AC. As with the switching power supply, the noise is created inside the power supply so nothing you do before it makes a difference.

Actually one bad thing happens as noted: we now have a bit of a ground loop/leakage with both AC regens at 60 Hz. Anytime you string another AC source with its own power supply, grounding, etc. you increase your risk of creating ground loops and that is what we see here. So don't think these regens help with ground loops. They can very well create them. And if they fix them, it is an accident and not by design.

The conclusion here is simple: neither power supply cares about how clean the incoming AC is. So whether you clean it some with P12 or a lot with my 9801 generator, it makes no difference. There is noise in the output of the power supply which the audio equipment filters before usage. It is that filtering that is important, not what is done on AC waveform.

Topping A90 Measurements
I imaging anyone spending nearly $6,000 on an AC generator, is also investing in state of the art equipment when it comes to noise and distortion. I decided to test my Topping A90 since a reviewer quoted by PS Audio tested a headphone amp with P12:
PS Audio Power Plant P12 Headphone Amp Review.png



Here is how it performs using raw AC input:

Topping A90 Measurements Headphone Amplifier.png


Same stellar performance we have seen before. Notice how the FFT shows no mains harmonic distortion, proving that it has effectively filtered them all. So it clearly needs to help from cleaner AC but let's give it that and see what happens:
Topping A90 Measurements Headphone Amplifier with PS Audio PowerPlant P12 AC Regenerator.png


Notice how mains leakage has increased a bit as I showed in pervious measurements. Fortunately it is still so infinitely low level to not be of concern.

I then ran a broadband frequency sweep, capturing noise+distortion:
Topping A90 Measurements Headphone Amplifier FFT with PS Audio PowerPlant P12 AC Regenerator.png


Again, vertical display is zoomed. Strangely, the PS Audio P12 (red) has made things worse here! We are losing about 1 to 1.5 dB of performance. To figure out why, I analyzed the full 90 kHz spectrum of the output of A90 while playing a 1 kHz tone:

Topping A90 Measurements Headphone Amplifier 1 kHz FFT with PS Audio PowerPlant P12 AC Regener...png


There is a spike at 68 kHz which is likely the switching frequency of some component inside the A90. Its level with raw AC is -122 dB which is extremely low so normally not a concern. But for some odd reason, when powering the A90 with PS Audio P12, it raises by 1.8 dB which is the difference we are seeing in measurements!

Not that it matters in grand scheme of things but it is interesting how our intuition is wrong in assuming that an AC regenerator always makes things better. It didn't in this case.

Why Owners Report Better Fidelity
There are countless people who buy these products and swear by them. How is that possible seeing that measurements don't remotely back them? Simple: improper testing. P12 is inserted in the system, listener pays more attention and now has a different impression of music. He hears more detail, more air, etc. He then decided that the theory of the power regen is proven. When taking it out of the system, expectation is that it will sound worse and it will. This is all part of being human.

A proper test would involve doing the above test blind. With analog devices like headphone amp, you should be able to move the power cable quickly between AC mains and P12 without the playback system needing initialization. Have someone do this type of quick switching (or slow if you like) and see if you can get > 8 answers right out of 10. If you do, then we have statistically significant results. Otherwise there is no there, there.

Edit: Listening Tests
I performed two sets of listening tests. One with headphones and one with speakers.

Headphone test chain was RME ADI-2 DAC driving Topping A90 Pre-amp using balanced connection. Headphone in use was the Dan Clark Stealth. I started to listen to A90 fed with raw mains and then switched to PS Audio P12. Immediate impression was a bit louder and dynamic. Switched back and now the A90 with raw power was that way. :) Switched back and forth half a dozen times and the two sounded the same. Everything I thought I heard with P12, I would also hear just as well with the raw AC.

Speaker listening chain was silent custom music server, to Matrix Sabre MQA DAC/streamer ($2,000), to Mark Levinson 532 reference (400 watts/ch - $20,000). Output drove my Revel Salon 2 speakers ($23,000). I started with Raw AC from the wall, feeding the ML 532 with a thin extension cord to really disadvantage it. The sound was superb with incredible dynamics and fidelity. Sometimes I forget how good my everyday system is. :) I then switched the power from ML 532 and ran a normal power cord to PS Audio P12. The P12 was driven using Pangea power cord. Immediate impression was lower fidelity. More compressed sound. Just less fidelity. I think I was biased by thinking that no way my giant amp could be driven by this little box. Of course I switched back to raw AC and heard the same sound as P12. :) Switched a couple more times and result was that there was no difference.

Net, net, there is no audible difference in these ad-hoc tests.

Conclusions
I hope you appreciate the comprehensive assessment that I presented to you above trying to tease out in every possible way what the P12 does. At high level, yes it is an AC regenerator capable of producing less distorted AC waveform. Strangely though, it adds noise of its own in low frequencies and doesn't perform anywhere close to my Lab AC Regenerator. My memory is that the older PS Audio AC regenerators were much better in this regard. So as an AC regen, the P12 is not that great of a device compared to what it could be.

The rest of the tests show why none of these power devices are capable of improving the output of our audio devices. They do nothing about noise generated by the power supply which is easily filtered in the audio device. You can't make your food taste better by washing the dishes you serve your food in multiple times!

Of note, deploying an AC regen causes power to be wasted, noise generated in the form of its fans, and reliability issues given the high powers and currents involved. You will incur good money shipping this unit back to the company to repair given how much it weighs (48 pounds/17 kilograms).

Before someone says, "but you haven't measured this and that," wonder why the company hasn't and published that! Send them your questions, not me. For a device that we can predict can't do anything useful based on simple engineering principles, we have done a ton to put proof behind our opinion.

Anyway, I can't recommend the PS Audio PowerPlant P12. I can't detect it making any improvement to your audio devices and costs a fortune to boot. Save your money and put it toward a better cause.

EDIT: video review posted:


Edit 2: Second set of measurements and power amplifier testing here: https://www.audiosciencereview.com/...-audio-p12-review-part-2-power-testing.31432/
-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
Last edited:

LearningToSmile

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Given the sort of audience that buys these things, if instead of a properly engineered piece of kit like the Topping A90 we would use some poorly engineered "audiophile" amplifier, is there a possibility that difference would be noticeable then? Though given the power supply results I'm assuming still no.
 

charleski

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For the genesis of this idea, here's a quote from Paul McGowan's book, 99% True, "Today, power conditioners are a dime a dozen—everything from Walmart surge protectors and computer power-backup boxes to sophisticated models costing many thousands of dollars, used by laboratories and audiophiles. But in 1997 there was almost nothing designed for high-end audio gear. That vacuum looked to me like an opportunity—I could start at the very beginning of the equipment chain, design and build a new box that would regenerate AC power, and market and sell it to audiophiles."

Uhuh.
 
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amirm

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Given the sort of audience that buys these things, if instead of a properly engineered piece of kit like the Topping A90 we would use some poorly engineered "audiophile" amplifier, is there a possibility that difference would be noticeable then? Though given the power supply results I'm assuming still no.
As I showed, the output of the power supply is not impacted by the AC noise and spectrum so this kind of thing has an extremely low probability of doing anything useful. Is there an odd device out there that can do better? Well, if it exists, it is the job of the company to find it to counter my testing. :)

FYI in the past I have tested tube amps and such. Those boxes are again generating their own noise and distortion which is unrelated to AC.
 

tonycollinet

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Great testing as ever.

But I think it would make sense to stop testing these overpriced paper lead sheet weights, until a manufacturer actually does their own homework and provides evidence they are more than just snake oil. You have enough tests done by now to demonstrate that they are universally redundant.
 

Prana Ferox

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I don't particularly want to be kind to this device but UPSes that are similar in concept frequently need some minimum load to produce 'clean' output. Testing it completely unloaded or with just a DAC hanging off of it might be worse than running it loaded. Of course people don't buy these things to hang a water heater off of so who knows what sort of steady-state output to use.

I would assume in the context of this device, "an improper voltage supply" probably means a small gas generator, or something off of 12VDC, that isn't really big enough for high current loads. You know, for the audiophile trying to clean up his tube amp power on his yacht
 

Kevinfc

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Amazing the stuff that so many bought into at such great cost. I was one, though not at nearly this cost. Now if you’ll excuse me, I have to go check if my RCA cables are connected in the proper direction.
 
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amirm

amirm

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I don't particularly want to be kind to this device but UPSes that are similar in concept frequently need some minimum load to produce 'clean' output. Testing it completely unloaded or with just a DAC hanging off of it might be worse than running it loaded. Of course people don't buy these things to hang a water heater off of so who knows what sort of steady-state output to use.
My lab generator was operating with the same load or lack thereof. In addition, the top use for these boxes are source products as power amps can be limited with them. So my testing is typical of its usage profile.
 

YSC

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This is a review and detailed measurements of the PS Audio PowerPlant 12 (P12) AC regenerator. It is on kind loan from a member and costs US $5,499.
View attachment 189600
PS Audio nails the industrial design of the unit. I really like the casework as well as the look of the various graphical meters as you see above. There is even network/Ethernet support to monitor them over time and remotely:
View attachment 189601
This is one heavy unit though despite its svelte height. Here is a shot from underneath:

View attachment 189602

Looks like we have a toroidal transformer on bottom right and power supply circuit to its left. Then on top is the AC regenerator which is basically a high voltage mono amplifier fed by a specific frequency (60 Hz in my instance). There are large heatsinks on the amplifier cooled by those two fans. I don't know if it sucks air from bottom or what. If it is, the feet are too shallow to allow good airflow. You better not put this on top of anything else that generates heat for the same reason.

After I took the above picture with the P12 on its side, I went to rotate it down and something really sharp poked and tore up my finger. Put it back up and noticed that there are two sharp points in the sheet metal (one indicated with the arrow). Not only is this dangerous from handling point of view but also is poor design as they can catch and bend in or out. The two sharp points should have been wider and connected to each other (vertically). The tip of my finger is hurting a bit still as I type this. :(

In case you are not familiar with this class of device, they take AC input, convert it to DC. That DC is then used to drive a power amplifier that is driven by mains frequency. Idea is that they can generate AC with lower distortion+noise than what the power company provides you. One wonders what cleans its own power supply if one needs a clean AC to drive audio equipment but we digress. :)

Company advertising makes lofty claims that are sadly not backed by any measurements:
View attachment 189603


"Sine-wave-perfect?" Nothing perfect exists in real life so that for sure is a stretch. How much we will see in measurements.

As usual there is also the claim of lower noise:
View attachment 189604

Again, if we can "expect lower background noise," why not show it to us in a measurement?

Being a high powered unit (think 800 watt amplifier), I worry about longevity and was reasonably happy to see a 3 year warranty. But then it had these exclusions:
View attachment 189605

Preventative maintenance? What would that be? Can't imagine they are asking the customer to open a unit lethal high voltages in it to clean those fans or circuits. The bigger issue is "connection to an improper voltage supply." Come again? I thought the purpose of this unit is to take improper AC supply and clean it up. And how would the customer know what is improper anyway?

Anyway, being an expensive product of its kind, the following testing is also a lot more expensive. To understand the flow, this is what we have here:

Raw AC Mains. This is what is powering my desktop computer, Audio Precision APx555 analyzer and any audio device I usually test. I measure this so we know what we are working with.

PS Audio P12 Output. The P12 takes raw AC and converts it to DC. It them modulates it with a sine wave with output regulated/nominal 120 volt. I measure this output and compare its quality to raw AC and my lab AC regenerator (BK Precision 9801).

Audio Power Supply Output. Almost every audio device also converts the incoming AC to DC. So I took both a switching and linear power supply and measure the DC spectrum of noise and distortion powered by either raw AC or PS Audio. If the theory of these products is correct, then the DC output of the power supply should be cleaner.

Analog Output of Headphone Amplifier. I tested a Topping A90 high performance headphone amplifier with both raw AC and PS Audio P12. Unlike the above tests, this is an actual test of fidelity and ultimately all that matters. The rest of the measurements help us understand what we are seeing here but ultimately they don't matter. Testing is performed both at one frequency and full suite of frequencies.

Let's get started.

AC Measurements
This is tricky business as we are talking 120 RMS volts (peak about 170 volts). This would damage the input stage of many measurement devices. Fortunately I have a differential AC probe (helps with not picking up stray signals/noise) that also has a 100:1 divider. This brings the voltage way down allowing me to use my Audio Precision analyzer with its full resolution to analyze AC power. This gives us far, far more accurate results than any AC line analyzer. First, we need to make sure the differential probe is not limiting the measurements so let's test it:

View attachment 189607

26 volt is output by Audio Precision APx555 and then looped through the differential probe. As you see, the voltage is divided down to 0.26 volt (100:1). The probe is creating just a second harmonic that is at -95 dB. Add some noise to it and our SINAD drops to 81 dB. For audio equipment that is not great but for measuring AC it is extremely good as what we are testing has far more noise and distortion as you shortly see.

So now let's measure the Raw AC in my lab:

View attachment 189608

Our AC waveform is distorted (tops of sine wave are rounded a bit) and noise added. If you look on top right, you can see what we have. The first tall spike is at 60 Hz which is the wanted frequency. But we also get a spray of harmonics at its multiples. We could treat this as a normal audio signal and compute its THD+N as show which is about 2%. P15 provides its own measurement but it underestimates it by a bit:
View attachment 189610

Maybe it is ignoring noise and just showing THD.

Now let's fee the Raw AC to PowerPlant P12 and measure what comes out of it:

View attachment 189611

We see a sharp reduction in harmonic spray with P12 resulting in our SINAD climbing from 36 dB (raw AC) to 67 dB (output of P12). We get a true THD+N of 0.46 which is much higher than 0.1 shown by P12 (0.1%). Fortunately we are still within the spec for P12 as I have copied and pasted in the center of the graph (< 0.5%).

I did notice raised noise floor though relative to our AC mains which surprised me. So I drilled down:

View attachment 189612

RAW AC is in blue, and once passed through PS Audio P12, in red. We see that the red has lower harmonics but has much higher noise floor across the full spectrum of audio.

Let's compare the same to my BK Precision 9801 lab AC generator (about US $2,600):

View attachment 189613

Notice how SINAD has shot way up to 65 dB now, courtesy of much lower harmonic distortion and noise. We can compare them again using the spectrum analyzer:

View attachment 189614

So as an AC generator, the P12 is quite a poor one. Granted, my 98091 is rated at 300 volt-amp and the P12 is 1000 so maybe we allow some difference in distortion but not this much.

The unit as shipped and tested by me comes in "high regulation" mode. It keeps the voltage constant at the expense of distortion. So I thought I change the mode and compare:

View attachment 189615

I am not seeing a difference. Maybe under heavy load it acts differently.

While on topic of not making a difference, there is a multiwave setting that goes from 1 to N. I changed that from 1 to 6 but it made no difference whatsoever in the output. I thought multiwave was for unit to generate different waveform than single 60 Hz. I like the company to show and document the waveform difference as you change this setting.

There is always an argument around these devices that they clean up noise above audible band. So let's test for that with 1000 kHz or 50X our audible band and see what is going on:

View attachment 189618

We see that the results are the same and not much is going on above 100 kHz anyway. The lab generator remains cleanest with P12 having higher noise floor at lower frequencies but lower distortions than AC mains.

Audio Power Supply Noise and Distortion Measurements
Let's start with the output of a small switching power supply that powers a Topping DX3 Pro which I had handy. Here is its spectrum when fed by my normal AC mains:

View attachment 189616

I have heavily zoomed the vertical scale so that we can see what is going on. At normal scale it would look like a flat line that DC would. We see the worst case of noise is a spike between 1 and 2 kHz. Its amplitude is at -65 dB which may be objectionable. But remember, this is the raw DC going into the Topping DX3 Pro. Secondary voltage regulators and filtering is used to clean this up before use. But let's go with it and compare it to when we power the power supply through P12:

View attachment 189617

I say no difference but the output of P12 seems a bit worse with our spike now rising a few dBs. That nit aside, none of the "nasties" have been removed. Reason is simple: bulk of them are generated in the power supply. The incoming raw AC was converted to DC inside this power supply and filtered. So what the P12 cleaned up was not material.

Another class of audio power supply is linear. For that, I grabbed the external DC power supply that came from my GRAS headphone measurement system. Here is its output when fed from raw AC (blue), PS Audio P12 (red) and BK Precision 9801 lab AC (blue):

View attachment 189624

The process of getting DC from AC involves first flipping the negative cycle of the AC sine wave to positive. This doubles the frequency of the mains input and shows up as a result as 120 Hz spike. We see that there is no difference between the three methods of input AC. As with the switching power supply, the noise is created inside the power supply so nothing you do before it makes a difference.

Actually one bad thing happens as noted: we now have a bit of a ground loop/leakage with both AC regens at 60 Hz. Anytime you string another AC source with its own power supply, grounding, etc. you increase your risk of creating ground loops and that is what we see here. So don't think these regens help with ground loops. They can very well create them. And if they fix them, it is an accident and not by design.

The conclusion here is simple: neither power supply cares about how clean the incoming AC is. So whether you clean it some with P12 or a lot with my 9801 generator, it makes no difference. There is noise in the output of the power supply which the audio equipment filters before usage. It is that filtering that is important, not what is done on AC waveform.

Topping A90 Measurements
I imaging anyone spending nearly $6,000 on an AC generator, is also investing in state of the art equipment when it comes to noise and distortion. I decided to test my Topping A90 since a reviewer quoted by PS Audio tested a headphone amp with P12:
View attachment 189635


Here is how it performs using raw AC input:

View attachment 189629

Same stellar performance we have seen before. Notice how the FFT shows no mains harmonic distortion, proving that it has effectively filtered them all. So it clearly needs to help from cleaner AC but let's give it that and see what happens:
View attachment 189630

Notice how mains leakage has increased a bit as I showed in pervious measurements. Fortunately it is still so infinitely low level to not be of concern.

I then ran a broadband frequency sweep, capturing noise+distortion:
View attachment 189632

Again, vertical display is zoomed. Strangely, the PS Audio P12 (red) has made things worse here! We are losing about 1 to 1.5 dB of performance. To figure out why, I analyzed the full 90 kHz spectrum of the output of A90 while playing a 1 kHz tone:

View attachment 189633

There is a spike at 68 kHz which is likely the switching frequency of some component inside the A90. Its level with raw AC is -122 dB which is extremely low so normally not a concern. But for some odd reason, when powering the A90 with PS Audio P12, it raises by 1.8 dB which is the difference we are seeing in measurements!

Not that it matters in grand scheme of things but it is interesting how our intuition is wrong in assuming that an AC regenerator always makes things better. It didn't in this case.

Why Owners Report Better Fidelity
There are countless people who buy these products and swear by them. How is that possible seeing that measurements don't remotely back them? Simple: improper testing. P12 is inserted in the system, listener pays more attention and now has a different impression of music. He hears more detail, more air, etc. He then decided that the theory of the power regen is proven. When taking it out of the system, expectation is that it will sound worse and it will. This is all part of being human.

A proper test would involve doing the above test blind. With analog devices like headphone amp, you should be able to move the power cable quickly between AC mains and P12 without the playback system needing initialization. Have someone do this type of quick switching (or slow if you like) and see if you can get > 8 answers right out of 10. If you do, then we have statistically significant results. Otherwise there is no there, there.

Conclusions
I hope you appreciate the comprehensive assessment that I presented to you above trying to tease out in every possible way what the P12 does. At high level, yes it is an AC regenerator capable of producing less distorted AC waveform. Strangely though, it adds noise of its own in low frequencies and doesn't perform anywhere close to my Lab AC Regenerator. My memory is that the older PS Audio AC regenerators were much better in this regard. So as an AC regen, the P12 is not that great of a device compared to what it could be.

The rest of the tests show why none of these power devices are capable of improving the output of our audio devices. They do nothing about noise generated by the power supply which is easily filtered in the audio device. You can't make your food taste better by washing the dishes you serve your food in multiple times!

Of note, deploying an AC regen causes power to be wasted, noise generated in the form of its fans, and reliability issues given the high powers and currents involved. You will incur good money shipping this unit back to the company to repair given how much it weighs (48 pounds/17 kilograms).

Before someone says, "but you haven't measured this and that," wonder why the company hasn't and published that! Send them your questions, not me. For a device that we can predict can't do anything useful based on simple engineering principles, we have done a ton to put proof behind our opinion.

Anyway, I can't recommend the PS Audio PowerPlant P12. I can't detect it making any improvement to your audio devices and costs a fortune to boot. Save your money and put it toward a better cause.

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

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Gave it a pass as it is a rare ps audio accessory stuff that actually do something they advertise! But regarding the conclusion that someone buys $6k of a power conditioning is supposed to have totl component I do disagree, usually they are the ones chasing after otl tube amp especially vintage ones, legendary in an era type, which I think these might be actually useful?
 
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