PS Audio DirectStream Power Plant 12

In the November 2018 issue of Stereophile, Jim Austin reviewed PS Audio's DirectStream Power Plant P20 AC regenerator ($9999). PS Audio had sent me the less expensive DirectStream Power Plant 12 ($4999), hence this review.

Why use an AC regenerator rather than plugging components straight into the wall?

Consider these two ways of powering an audio system:

1) AC power is available at a precise standard voltage and frequency (in North America, these standards are 120V and 60Hz) that do not vary with time of day or load, with no distortion of the 60Hz waveform, a complete absence of electrical noise, and limited in terms of current flow only by circuit breakers and fuses. Audio equipment could then be designed and manufactured assuming the invariance of these characteristics of AC power. Such a power amplifier, say, could do its job without its owner ever being concerned about the flaws in less-than-perfect AC showing up in the amp's output as audible distortion.

2) Alternatively, while nominally 120V/60Hz, the actual AC power available varies with the time of day and the demands placed on the power supply, and its waveform may contain both noise and distortion products. It is then up to the designers of audio equipment to include in their products tolerance of deviations from the standard voltage of 120V, as well as ways to filter out AC-borne noise and distortion.

Although 1) represents an ideal that would benefit audio equipment manufacturers, as Nelson Pass said, in Jim Austin's interview with him in the November 2018 Stereophile, "We try to build equipment that puts up with dirty AC lines."

PS Audio's approach (footnote 1) to the problem of dirty power lines is the Power Plant—basically, a sinewave generator combined with an audio amplifier. The Power Plants are designed to accept the power available from the wall receptacle, whatever its characteristics, and to output "clean" power at the nominal rating of the electrical supply. I reviewed the first Power Plant, the P300, in December 1999. That product was an overwhelming success, and virtually created the product category of "AC regenerator." Since then, PS Audio has developed a range of Power Plants, with models varying in output, and refined the execution of the basic concept. I reviewed the Power Plant Premier in February 2009, and through the years, one Power Plant or another has been part of my audio system, most recently a DirectStream Power Plant 5 (footnote 2).


The DirectStream Power Plant 12, or P12, can supply a continuous 1250W compared to the P20's 2000W output. Jim Austin's system includes such power-hungry amps as PS Audio's own BHK Signature 300 monoblocks, but I thought the P12 would be an appropriate match for my more modestly powered system, which includes a McIntosh Laboratory MC275LE (75Wpc) and PS Audio's Stellar M700 monoblocks (350W, class-D output stage), and might make for an interesting comparison with my P5. The P12 has the same form factor as the P5, but PSA says it's a completely new design. The P5 uses a PCM-based sinewave generator; the P12's sinewave generator is DSD-based, its design borrowed from PSA's DirectStream DAC.

Pixel peeping is a term used in photography, often derogatorily, to refer to the practice of examining images in extreme detail on a computer monitor. There is no correspondingly pithy term for the audio equivalent of pixel peeping, but the practice certainly exists. I've been guilty of it myself, usually in A/B comparisons involving small differences. However, rather than sit in my listening chair and listen intently to how the amount of detail produced by Product A compares with that produced by Product B, I generally prefer to just listen to the music—not always sitting in my listening chair—at volume levels that vary with my mood. Then, if there's no immediately obvious difference in what I hear with Product A vs what I hear with Product B, I move into pixel-peeper mode and start making more specific controlled comparisons.

In this case, to calibrate my ears, I first listened to the system with the Power Plant 5 as the source of power, just playing a variety of CDs, and ending with the überfamiliar Best of Chesky Jazz and More Audiophile Tests, Volume 2 (CD, Chesky JD68). The sound was very good indeed: detailed, well balanced, with precise imaging. To beat this, the Power Plant 12 had its work cut out for it.

I then turned off all the system components and the P5, swapped power cords from P5 to P12, turned on the components and the P12, ran the P12 through its CleanWave degaussing function (as I'd done with the P5), waited 10 minutes, and put on the Chesky test CD.

No contest! As good as the system had sounded with the P5, with the P12 there was a major step forward in overall realism. With no change in volume setting, the sound was more dynamic. This was particularly noticeable with audiophile blockbuster CDs, such as Reference Recordings' Tutti! orchestral sampler (RR-906CD), but it was also evident with more intimately recorded music, such as soprano Sylvia McNair and pianist Andrè Previn's (with double bassist David Finck) Sure Thing: The Jerome Kern Songbook (CD, Philips 442 129-2).

In my initial bout of listening, amplification was provided by the PS Audio Stellar M700s, and as it's likely that PSA "voiced" those amps with a Power Plant in their reference system, the P12 and M700 might be expected to act synergistically. And might it also be that amps with a class-D output stage, such as the M700, are particularly sensitive to the purity of the AC, but that this would not be the case with amps of very different design—say, my own McIntosh MC275 LE?

The improvement wrought by the P12 was, if anything, greater with the McIntosh. The midbass-to-low-bass region was clearer, with bass drums and timpani seemingly having a more solid foundation, and transients generally having crisper onsets and more rapid decays. The MC275 LE seemed to lose some of its "tubey" characteristics—it sounded more neutral, more like the real thing.

The P12, like the P5, has an LCD screen that shows, among other things, its performance, with displays of Voltage In/Out and THD In/Out. With no music playing, the Voltage In was 129.3V—substantially higher than my house's nominal supply of 120V—and the Voltage Out was 120.3V. The P12 was clearly doing a good job of regulating the AC voltage. THD In was 3.1%, THD Out was 0.1%—again, impressive performance. However, the P5 was nearly as impressive: 125.8V Voltage In to 119.8V Voltage Out, and 3.0% THD In to 0.21% THD Out. Given the clearly audible superiority of the P12, I expected the measured differences to be greater. What gives?

Summing Up
I asked Paul McGowan, CEO of PS Audio, to comment on the apparent similarity of the measurements. He said that the big differences were not in distortion as such, but in how the distortion would vary depending on incoming level and use. The P12 and its siblings are more resistant to influence by these factors. Perhaps even more important is the lowering of output impedance, from about 0.05 ohm in the previous generation of Power Plants to 0.008 ohm in the current models. McGowan acknowledged that the difference "might not seem like a lot, but it is a big deal," the lower output impedance resulting in greater energy storage, peak current demand, and tighter energy regulation. "When an amplifier demands a quick burst of transient power, the straight wall socket can't deliver it without dipping in voltage," he explained. "And if a passive conditioner is attached, that gets even worse. But when the regenerator is there, it delivers the energy without batting an eye—and that's where the magic happens."

Magic, indeed!

Footnote 1: PS Audio, 4865 Sterling Drive, Boulder, CO 80301. Tel: (720) 406-8946. Web:

Footnote 2: The P5 is a smaller version of PS Audio's P10, which Jim Austin reviewed in July 2016.

Bogolu Haranath's picture

Have to believe in ........

"Magic" ......... Olivia Newton-John :-) .......

ok's picture

ON-J happened to be the granddaughter of the unassuming genius Max Born, the one man behind all things quantical.

tonykaz's picture

How can a Reviewer critically evaluate High Performance Music System Electronics if the Supply Voltage & Amperage is Questionable and/or Unreliable?

Can we presume an Amplifier is designed and built with an adequate Power supply ? , probably yes within Dollar Constraints.

Can we presume our favorite Reviewer has reliable Power on tap at his house outlet ? , maybe not.

In Fact, we can probably assume that a household outlet will NOT have the High Quality Regulated Energy that a Engineered Power Source will reliably deliver.

So, I ask, how can a reviewer evaluate an if the Power Source is doubtful or evaluate the entire Music System's abilities to reproduce delicate musical passages?

Seems like these PS Audio Power Plants are foundational elements in a High Performance Music System. Prices starting around $2,000

Stereophile finds another Winner !

Tony in Michigan

jeffhenning's picture

With all due respect, reviews such as this are of no use to the reader.

It sounds wonderful to you and apparently its technology is so advanced that you can't distinguish it from magic. So what?

Just once, I would love to see one of these reviews exhaustively measure one end component that's hooked up to it to see whether it (the cable, conditioner, etc.) improves the sound of the end component in any objective, verifiable and non-anecdotal way. It could be an amp, a pre or a D/A.

Of course, they never do that (they being both reviewers and manufacturers).

Since a lot of science rather than magic is involved in all of this stuff (at least, the better stuff), it would be fantastic if the reviews and claims were not based on faith.

Furman is the only power product manufacturer, to my knowledge, that supplies real proof to the efficacy of their equipment. They supply specs and graphs.

I have no doubt that supplying clean power to your system improves its sound. Whether you have to spend $5K to accomplish this is not something I'll take as proven...not by a long shot.

Long-time listener's picture

After casting doubt on whether claims made for this PS Audio product are verifiable, the reader then comments, "I have no doubt that supplying clean power to your system improves its sound." That seems contradictory to me, but anyway...

I too might have doubts about the $5000 price tag, when there are companies such as NAD who seem able to provide tremendous value for the money in their products. But I don't have any doubts about whether these PS Audio products improve the sound. I had an earlier model, the Power Plant Premier, from I guess maybe 10 years ago, and it cost $2000 at the time. I only used it on my front end stuff, but even then the difference in clarity, color, texture, and presence were so audible that the improvement was, as you say above, beyond doubt. The problem was that it broke down several times in rapid succession after I bought it. I got tired of having it fixed and eventually I just left it out with the trash. I now use a passive PS Audio product, their Dectet distribution and filtering panel, which again provides quite audible improvement that I'm more or less satisfied with. If I had the money and I wasn't worried about dependability, I'd buy one of these new Power Plants.

Archimago's picture

Agree with the points made here.

From the perspective of the consumer, there are 2 things:

To answer this question, there's absolutely no reason not to try some measurements! Maybe create some kind of standard test bed where connected to the electrical line to an amp or DAC are hair driers running or doing a load on the washer/drier. Demonstrate that the DAC noise level decreased and maybe the distortion decreased on the amp when other devices are active.

Even if (1) is proven to be true that this product provides benefits, are we sure that the electrical outlets at home can benefit? This will likely vary between countries, counties, cities, time of the day, etc... Also home construction, wiring, outlet quality will all play a part. This is where consumers will need to decide on the value of the devices for themselves.

But at least prove as per (1) that they actually work to improve output from hi-fi gear first before recommendations are made.

Surge's picture

These PS Audio regenerators show you all the stats you need on their display. So your concerns were addressed. You see incoming THD and voltage and outgoing, among other stats. Everything you need to “believe” this is science is there.
These devices are essential, if you have the budget for them.

Glotz's picture

So are measurements. Furman is not the only one... Shunyata Research and many other prove through measurements.

BUT, if you don't trust a 30 plus year reviewer to tell you what he hears and adhere to the truth...

NO magazine is going to help you.. in fact, nothing will.
All he believes are his eyes
And his eyes, they just tell him lies'... Dylan

Bogolu Haranath's picture

".... and his brain has been mismanaged with great skill" :-) .........

invaderzim's picture

"Shunyata Research and many other prove through measurements."

They only measure the power coming out of the regenerators and never the audio components plugged into the regenerators. If the power supply in your amp cleans up the power coming in just fine then what use is the power cleanup before it?
If all my faucets have built in water filters and I put a $20,000 water filtering system on my house's water supply inlet and the water comes out of the faucets exactly as clean as before then the central filter, while doing a great job isn't improving anything. Granted I could just taste the water and go "It tastes so much better now!!!" Or I could have it tested to see if the final product is better.

The reviewer can certainly be adhering to the truth they believe but expectation bias is real and has been shown over and over to affect people's impressions of things. I'm sure he thought there was that improvement. I've thought components were amazing improvements before but when I switched to blind A/B testing I couldn't pick the 'better' component more than 60% of the time. If this improvement is so incredible in his test then it should easily be able to show through blind A/B testing.

What would be so refreshing in the audiophile reviewing business is just a bit of skepticism a bit of testing to go along with the swooning over the magic. Like the old bumper sticker said "be careful that your mind isn't so far open that everything falls out"

Long-time listener's picture

"...expectation bias is real and has been shown over and over to affect people's impressions..."

Let's not pretend we're experts on psychology. While I've experienced expectation bias myself, I've also found that it's usually a very short-term thing. For example, I used to use tone controls sometimes. I would think, "not quite enough bass." I'd turn up the bass and think "ahh, that's better, and go back to typing at my computer. Then I'd think, "Hmm, still not enough bass." I'd turn it up some more, think the same thing, then go back to work again. This would happen several times--until I suddenly realized I was in "tone defeat" mode. So I TEMPORARILY thought I was hearing more bass, but after a short time, my hearing told me that no, I wasn't hearing any more bass. The psychological moment passed, and the natural accuracy and discrimination of my hearing took over, and served me well. I just don't care about psychological effects or the double-blind tests used to overcome them. What I care about is whether I hear something consistently over a long enough period of time, in which the natural accuracy and discrimination of my hearing will work dependably. If I hear something under those conditions, then it's worth considering a change in my system.

Bogolu Haranath's picture

Similar phenomenon is 'placebo effect' :-) ..........

Long-time listener's picture

I think you might be misunderstanding my post. Whether you call it expectation bias or the placebo effect, what I'm saying is that I believe such things are actually pretty easy to overcome for serious listeners. If you just relax and listen without preconceptions, and give yourself enough time, your ears will do a pretty accurate job of hearing.

Bogolu Haranath's picture

Agreed :-) .......

Surge's picture

The power supply in your audio gear does NOT clean the power. That’s your assumption, and it’s wrong.
I have $50K amps and pre-amps and their performance is improved with the PS Audio P5.
Amps will CLEAN the power, but they cannot REBUILD it.
What’s coming out of our walls is SH~T - and it degrades when you draw more current from it. So when your amp tries to play that high or that explosion, the incoming power quality goes downhill in that very moment you need it to be perfect.

RichTheWizard's picture

Dear Mr. Surge: {Current? Voltage? Ha!} To be precise: I'm buying a, PS Audio P20 Power Regenerator. It's mine; if I want to call it a, `Regurgitator,' I will! In a weak gesture, attempt to placate the disgruntled fellow above, one good reason to buy my Regurgitator, is that it has a LOT of outlets on the back, several high current! Some wall voltage is delivered with `flattened tops & bottoms;' I don't understand how a passive device can restore this! I can tell that you're a gentleman {principally because we're in agreement!} Therefore, & to keep you / us, out of trouble: `Sh-t' obviously means, `shift,' as in, We worked on the Swing Shift. In the Navy, I was on a: SH - I - P TransporT. In elementary school, I was the SHiesT studenT! In Sports, I developed a "SHinsplinT!" A SHipwrighT, worked on my, SHiP! Get back to me for more! I'm waiting for the SHipmenT! If it doesn't arrive, there will be, no SHipmenT!

RichTheWizard's picture

Dear Mr. Surge: {Current? Voltage? Ha!} To be precise: I'm buying a, PS Audio P20 Power Regenerator. It's mine; if I want to call it a, `Regurgitator,' I will! In a weak gesture, attempt to placate the disgruntled fellow above, one good reason to buy my Regurgitator, is that it has a LOT of outlets on the back, several high current! Some wall voltage is delivered with `flattened tops & bottoms;' I don't understand how a passive device can restore this! I can tell that you're a gentleman {principally because we're in agreement!} Therefore, & to keep you / us, out of trouble: `Sh-t' obviously means, `shift,' as in, We worked on the Swing Shift. In the Navy, I was on a: SH - I - P TransporT. In elementary school, I was the SHiesT studenT! In Sports, I developed a "SHinsplinT!" A SHipwrighT, worked on my, SHiP! Get back to me for more! I'm waiting for the SHipmenT! If it doesn't arrive, there will be, no SHipmenT!

RichTheWizard's picture

I'm buying, `the best,' that I can reasonably afford. Along this end, I'm buying the PS Audio P20 power AC `fixer - upper,' & their best D to A converter. I, personally, like the, `synergy,' of using as much of the same manufacturer's quality gear, as possible. The PS AUDIO D to A Converter costs about $6,000. Their best CD Transport is $6,500, but prices may {or may not!} increase. There are occasional sales, for members of their, `family.' Any suggestions? {Elsewhere, is mentioned that he `only' has the P 15 power plant. How cheap, with a $500,000 turntable!

RichTheWizard's picture

Depends on how `picky' one is! There are, `semi - logical' limits, mercifully! You mentioned: water. In the general Los Angeles area, I have two locations with Hague quality water purification units. These are each `reasonably sized' tanks & the best crystals to use, are potassium (or next, salt. I prefer potassium - very nice, though a little more expensive). I don't need to `double this.' Similarly, I'm buying a PS Audio Power `regurgitator,' and I CAN NOT `daisy chain' another unit, of any kind, including passive. I'm also buying a special power cord, & it IS NOT recommended to, daisy chain, combine these in series. Buy the longest, needed. Same with connecting cables. There are, therefore, limits on what one can spend. Even on, `pretty good,' gear! I like your water comparison, though. {I'd hate to think of how much gear has been damaged, destroyed in the East, New York, by the flooding! Despite your analogy, electronic gear & moisture, water, rain, even if the equipment is turned off & unplugged, don't mix!}

Astolfo's picture

If you dont believe the PS readings before and after. then testing it is as simple as plugging a vacuum in the same outlet and play some music. tell me what you listen with the vacuum on the outlet and off, with the vacuum on and off. I can tell de difference a 100 times out of 100, my friends can tell too. the fact is that the concept of the PS plants is used in many labs with extremely sensitive instruments. These PS units work like a battery in a car. you could run a car with 10amp battery but not start it, or run a big stereo, lights etc. your alternator would be running all the time a fail a lot sooner. If you put a couple of batteries in your car the voltage drop when you start the car, or any equipment will be significantly less than with one battery. This concept is not magic, it has been used for decades and centuries.
My distortion into my house is between 3-4.5THD depending the day and what it is going on, both measured by a fluke and the PS; on the other side is ~0.1. that alone for me is worth the $. Are PS reliable? No way, and yes it SUCKS that people don't scream about the PS Audio ps quality and that these reviewers do not do long term runs and call the manufacturers out. For example a $5K record cleaning machine that lasts 2 years and you cant replace a pump is plain and simple ridiculous.
If Paul had an ounce of self respect would bring the quality a hundred times, he owes it to his legacy and his customers. I have a PS20, they sell it for $10K, they have sold a butt load of them, the components do not amount to more than $800-$1000. So why PS Audio quality is so bad is hard to understand.
But the PS powerplant does what it claims, now not every system will benefit, but every single component in my system in the USA does and a lot, in Spain the gains are not as much, but still significant.

ok's picture

..for a total hardware replacement –If convenient– of an old house’s electrical installation. Nothing really exotic: it actually costs less than an equivalent power conditioner while the results are even visible on the tv set; plus a brand new electrical hardware installation.

Charles E Flynn's picture

How to install a dedicated AC line

Surge's picture

Except it doesn’t solve the problem. It may help isolate your own house’s degradation from other appliances, etc, but it is not going to fix the garbage power coming into your house — and that’s the crux of the problem.

googoogjoob's picture

these powerplants do COMPLETELY solve the problem of the garbage power coming into your house. thats the very point. your garbage electricity powers a generator creating you brand new perfect, regulated, virgin power. problem solved. the results are easily discerned. free 30 day trial. nothing to lose but a little face.

Jason P Jackson's picture

Magic indeed.

goodfellas27's picture

I got me a Tripplite IS1800HG medical grade power isolator without the audiophile labels and BS price that isolates my system from all the power line noise for a fraction of the price. Now that's magic!

Surge's picture

It’s a nice low cost first step, for sure!

But you’re not REBUILDING the power. In my case, THD in is 4%. THD out with the P5 is 0.1%.
A nice outlet is still going to give you ~40X more distortion, not to mention voltage fluctuation, noise, etc.