I'm no stranger to PS Audio's line of Power Plant AC regenerators. About 20 years ago they introduced their first Power Plant, the P300, and I was one of the first to purchase a unit. I was suffering lousy AC coming from the power outlets in my home, and my stereo system sounded lousy because of it. Even though my system wasn't anywhere near as nice as it is now, it was still a decent high-end system. During the evening hours I thought it sounded fabulous. But in the middle of the day I likened it to the sound of the transistor radio I used when I was 8 years-old. The P300 was my saving grace. It didn't have enough power for all of my equipment, its recommended maximum load was about 200 Watts, but when I connected my front-end gear into it I just about had a heart attack. Here was the sound I was searching for!
After only a few months of use PS Audio introduced their Multiwave circuit, which I immediately ordered and installed. With it I reached a new level of sonic nirvana. A short time later I acquired a rather large PS Audio Power Plant P600, which was able to handle a recommended load of 720 Watts, which translated to being able to connect much more gear, and my system sounded even better. I still have both the P300 and P600. I use the P300 as a speed-controller for my turntable, not only because it provides my turntable with a perfect sine wave to the turntable's AC synchronous motor, but because by changing the frequency on the front panel of the Power Plant it changes the speed of the turntable. During all these years the P300 only failed once, which I wasn't too surprising since I used it almost every day for about twenty years! It took PS Audio only one day to fix, that is, after a short time traveling back and forth from the West Coast.
Before I had the P300 in my system, I had tried other power conditioners, but since they all work by merely filtering the dreadful AC power coming from the wall, there is only so much they can do. PS Audio takes the AC wall current, converts it into DC, and then back into AC, providing pure AC power. The process is a bit more complicated than this short explanation, but that's basically how it works, not by simply filtering the AC power. The PS Audio Power Plant is not a power conditioner. It is an AC regenerator. And the results speak for themselves.
The Power Plants regenerate power with Class A/B power amplifiers with a sine wave generator for an input. PS Audio claims that the methods in which they convert the AC to DC and back to AC is at least partially proprietary, but essentially, the AC/DC conversion is done with a standard full wave bridge rectifier and a load of capacitors. The DC voltage powers a large multi-transistor output Class A/B power amplifier that serves as the output to all the receptacles. That's the other difference between the three Power Plant models although they all use hospital grade outlets, it's the number of outlets that differ the P12 has eight outlets. The P15 has 10.
The beefy P20 reviewed here has 16 hospital grade outlets. The oscillator in the P20 is a DSD based instrument digitally phase lock looped to the incoming AC frequency to make sure the oscillator tracks perfectly. Paul McGowen, founder and Grand Poohbah at PS Audio, says since they have been designing and building these regenerators for all these years, they have found that the major sonic benefits of using their AC regenerators are not only due to the removal of noise from the AC (even though they do), but from "lowering the impedance and the replacement of missing energy".
Since none of these things can be accomplished with passive power conditioners that only filter the AC, which can remove noise but obviously do not regenerate the power, instead, the Power Plants provide fully regulated AC. He goes on to say, that this lowers the distortion and tightens the regulation, lowers the impedance and provides better sound for one's system. The Power Plants add energy back into the signal, and that is measured by the lack of the amount of distortion that is present on the sine wave (there is a distortion analyzer built into the P20). On a shared power line, the sine wave gets clipped, or at the very least, distorted. The P20 provides up to 60-amps of peak energy, which goes missing when many are sharing the same power line. Even in from the electronic equipment in one's home. And from all your equipment plugged into the wall.
Passive conditioners have no way of providing the missing energy, cannot lower the impedance, and can only filter the AC that the power company is providing to you. So, I guess the PS Audio Power Plants are exactly that, your very own power plants for your system. Without a Power plant, equipment connected to the AC line can dynamically modulate the power line with the music: big peaks of the stereo system pull down the line voltage and cause a type of modulation distortion. The P20 Power Plant corrects this by providing your system with its own power.
The next screen has the P20's overall performance data. Here one can view how the THD output is reduced and the output voltage is a stable 120 Volts. Next up is the "Status" screen, where it not only displays the voltage, mulit-wave strength, phase tuning, auto tune, mode, and dimmer, but where one can adjust these settings. Throughout the review period I had no reason to adjust any of these settings other than the dimmer, as I didn't want the screen to be on at all times. The screens were really no use to me because I had no reason to adjust anything, other than turning it off. The default setting allowed the P20 to do its stuff, and simply regenerate the crap that the power company was providing to my home.
The last screen is the Network Screen. Here one can see the P20 IP address and other network information if an Ethernet cable is connected to its rear panel. PS Audio says that this connection "provides extended functionality benefits", and they also recommend that one install a ferrite noise suppressor onto the Ethernet cable close to the unit for proper functionality. Again, the P20 is a beast of a component, and this is not just because it weighs close to 100 pounds.
And so, the results of connecting all the front-end equipment and preamplifiers was that it was rather obvious that there was a marked improvement in the sound quality that was coming from my speakers. This was both a good and a bad thing, as I thought my system sounded pretty darn good without an AC regenerator. The good thing was that my system sounded marvelous when connected to the P20. The bad thing was that I thought it sounded good before, and when I considered how much the asking price is not only for each component, but the entire system when it is all added up. So, it was a bit of a let-down to realize that even though mine was a quite a pricey system if one added up the original selling prices of all my gear yet a lousy AC regenerator could be connected to make it sound even better. It's not like I've never experienced this type of improvement before.
Earlier in the year I reviewed the massive Stromtank S2500 battery power supply. This component is not an AC regenerator in the same sense as the PS Audio DirectStream Power Plant. Instead, the Stromtank S2500 is a series of lithium-iron-phosphate-cells, and so this enables one system to run completely off the grid, using batteries to power one's system. The Stromtank I reviewed is the smaller of two models offered yet cost twice as much as this PS Audio P20 AC regenerator I'm reviewing here, and four times as much as the PS Audio P12 AC regenerator. The result of using the Stromtank was indeed sonically impressive.
For $20,000 it ought to sound impressive. For $30,000 one can have the pleasure of using the larger model. If you have the money, I say go for it (but not until you speak to me first, so I can arrange to for you to give to some very worthy charities). Since I don't have the Stromtank in my system, and have not for quite some time now, I cannot give you a detailed account on how I think the PS Audio P20 DirectStream differed in sound from the Stromtank. But given their huge price difference I don't think it would be very useful, that is, unless I concluded that there was no difference between the two. My sonic memory is pretty good, though, so I'm confident in saying there the is a difference is the sound between the two. And the Stromtank comes out on top.
But again, given the price difference between the two, using the Stromtank ought sound better. But, there were many similarities between the two. Both brought out what I think are the strong points in my system. Using language that non-audiophiles and audiophiles alike will likely understand, connecting my equipment to the PS Audio DirectStream Power Plant 20 AC regenerator made it sound like my system was using anabolic steroids. It sounded the same, but much better.
I used two different linestages while the PS Audio P20 powered the system, a vacuum-tube powered Nagra Classic Preamp and a solid-state Merrill Audio Christine Reference, and only a solid-state Mark Levinson No. 523 for a very short time. I used Accusound XD cable to connect the front-ends to the linestages, and the linestages to the Pass Laboratories X350.5 power amplifier. Accusound speaker cable ran from the power amp to my Sound Lab Majestic 545 full-range electrostatic loudspeakers, their ultra-lows augmented by a pair of Velodyne HGS-15b subwoofers. The listening room has two dedicated power lines running directly to our home's circuit panel. There are acoustic treatment panels on the walls, and many LPs on many selves lining the walls which also prevent sound waves from projecting where they shouldn't.
I connected every bit of equipment to the PS Audio P20, except the power amplifier. I tried connecting the power amp to the P20, and it didn't blow its fuse (the amp's or the P20's) but it seemed to me that the X350.5's dynamics sounded more than a bit restricted in range when connected. I talked to someone at Pass Labs about this, and was told that this is not uncommon, that their experience has been that their larger power amplifiers sound better if plugged directly into the wall receptacle. I asked why and was given a short lecture on the prowess of the X350.5's power supply, and again how it doesn't need to be fed anything but power from the wall socket. I didn't argue because I don't have anywhere near the kind of engineering experience the fellow on the other end of the phone line at Pass Labs, so I took his word for it.
I also didn't connect my subwoofers to the PS Audio P20, as I felt there was no difference when I did, but I did connect the Sound Labs speaker's generic power cables to the P20. They don't draw that much power, in fact, I'm fairly sure electrostatic panels only need power in the same way our audio components do, they simply need electrical current to run through them to allow their electrostatic panels to work properly, and so it was not surprising that I didn't hear a difference if they were connected to the P20 or not. But the front end and preamps connected to the P20 made my system sound much, much better when connected to the P20, and so that's where they stayed for the entire review period.
PS Audio adds a THD (Total Harmonic Distortion) analyzer on the Power Plant's front panel. Using the MultiWave adds some third harmonics to the top of the sine wave on the output. As was mentioned, this increases the charging time for equipment and increases the level of sonic performance of the equipment connected to the Power Plant. But why add harmonics if the Power Plant is supposed to remove them? PS Audio says that understanding how the Power Plant works might help in explaining why the harmonics are there in the first place. The dirty AC coming from the wall receptacle has the top of the sine wave cut off, most because of too many users on the AC line. These harmonics are displayed on the P20's front panel. The P20 repairs this problem by adding missing energy back into the AC, and at the same time replacing the flat-topped sine wave with a perfectly smooth sine wave that is free of harmonics.
In PS Audio's words, "It isn't the problem of the flat sine wave, it is the missing energy used to charge your equipment which the Power Plant repairs by rebuilding new power. MultiWave creates more energy by replacing the missing energy by extending the charging time of the peak of the sine wave once we replace the energy. This is done by adding some pure third harmonic, but the key here is its full energy. So, there is nothing missing in the sine wave." I've found that some equipment benefits from the MultiWave technology, some doesn't, and at least one component's transformer made a buzzing sound with one of the Multiwave settings. And so, I changed the setting.
The new PS Audio DirectStream Power Plant 20 AC Regenerator takes what was good with those older Power Plants, and the engineers and designers seem to have been able to boost the performance of what seemed like simple devices (they're not) and make them even better! Recommended if you can afford it, but please first donate to your (or my) favorite charity.