PS Audio Power Plant Premier AC Regenerator By Robert Deutsch   •   February, 2009 Determining whether an idea is brilliant or off the wall is often a matter of perspective—and of looking at the results that follow from the idea. Take the notion of AC regeneration. AC is what comes from the wall socket, courtesy a network of power-generation plants, and it's specified as having a certain voltage and frequency, with the amount of current limited by fuses or circuit breakers in the electrical panel of the house or apartment. Audio components—other than those powered by batteries—are designed to convert this alternating current (AC) to direct current (DC), then produce variable AC that drives the speakers to produce a facsimile of that signal. In short, AC provides the raw material used by audio components to do their job.

Designers of audio components assume that the AC power source will have certain standardized characteristics (in North America, a 120V sinewave at 60Hz), and configure their prototypes' internal power supplies with this in mind. These supplies are usually designed to filter out unwanted high-frequency distortion components that may be present in the AC power source. A separate AC line from the electrical panel, dedicated to serve only the audio system, is considered a good thing, providing a degree of isolation from household appliances and lights that can interfere with the purity of the AC power.

For decades now, devices have been sold that are claimed to purify or "condition" AC, filtering out potential interference-causing parts of the AC waveform and thus easing the work of the audio components' power supplies. Many audiophiles have found these devices helpful to the sound; others have rejected them because of what they felt were undesirable audible side effects, such as an obscuring of detail or a reduction in dynamic range, and because tests have often shown that their measurable effect on the AC waveform was minimal.

Power to the people
Enter the PS Audio Power Plant, originally introduced in 1997 as the Model P300. Paul McGowan, the P of PS Audio (the S, Stan Warren, left the audio business some time ago), has argued that the best way to get rid of undesirable components of the AC is not to try to filter them out, but to "regenerate" the AC supply altogether with a power amplifier that outputs pure 120V at 60Hz. It's like having your own power plant in the home—hence the name. (To carry the analogy further, perhaps the best thing would be to have your own power generator, fueled by gas or coal. Then you'd really be free of the vagaries of the electrical power grid.)

The output of a PS Audio Power Plant is regulated 120V AC at 60Hz (50Hz in Europe) with low distortion, the maximum power output depending on the model (300W for the P300). I reviewed the P300 in the December 1999 Stereophile (Vol.22 No.12); John Atkinson's Follow-Up appeared the following May. My conclusion, with which JA concurred, was that the P300 worked as claimed. It wasn't just a matter of less noise, as expected, but also a generally smoother, more relaxed sound, with such goodies craved by audiophiles as "blacker blacks," and no loss of resolution or impairment of dynamic range. The P300 and its higher-powered variants have been extraordinarily successful, selling lots of units, winning numerous awards from audio magazines, and finding homes in the reviewers' systems—including mine and JA's. In the February 2006 issue (Vol.29 No.2) I reviewed the P500, noting its improvements over the P300.

Like any audio component, the P300 had its limitations. The first was of power output: 300W may be fine for source components and preamps, but it's not enough for any but low-powered amplifiers. The higher-output P500 produced 500W—better, but still not enough for the big power amps—and if you went for the top-of-the line P1200 (1200W output), you had a 150-lb component to contend with—and a corresponding increase in your electricity bill. There was also the matter of heat: the P300 ran hot when working hard, and its cooling fan was noisy. The P300 had only four outputs, which meant having to use a power bar in complex systems—not an ideal solution.

Over the years, the design of the Power Plant evolved, with new features such as MultiWave (an alternative to the standard AC sinewave, with a waveform that's supposed to make components' power supplies work more efficiently) and CleanWave (an AC power equivalent of variable-frequency signal-degaussing devices). And, to respond to the needs of audiophiles not yet ready to plunge into the world of power regeneration, PS Audio continued work on passive devices, such as the balun-based Ultimate Outlet (which I reviewed in December 1991, Vol.24 No.12), and the ingenious Noise Harvester, which shunts some of the power line's high-frequency noise to an LED, effectively transforming electrical noise into light. (I use Noise Harvesters in my home-theater system, to good effect.)

Premier Primer
Now we have the Power Plant Premier ($2195), which PS Audio calls "the world's first and only low distortion, high efficiency AC power regenerator." The key part of this claim is "high efficiency." Earlier Power Plants consisted of a class-AB stereo amplifier with an efficiency of about 50%—which meant that they had to be very heavy if they were to output substantial amounts of power, hence current. The Premier's maximum output is 1500W; a Power Plant of the previous design that produced this much output would weigh about 200 lbs. Instead, it's a far more manageable 35 lbs. This is the result of a new amplifier design that's 85% efficient—but is not, as might be expected, class-D, which PS Audio determined would produce too much noise for this application. Instead, it's a development of the usual class-AB amplifier. What's special about it is a new tracking power supply designed by Bob Stadtherr, PS Audio's head of engineering, for which the company has received a patent. According to Paul McGowan, the concept of the tracking power-supply design is "elegantly simple, and its execution is breathtakingly complex to make it work."

Starting with the new higher-efficiency amplifier design, the slim, stylish chassis of the Premier (said to be based on the BMW automobile) includes every bit of AC-related technology that PS Audio has learned in the past decade. There is sophisticated spike and surge protection. (Other protective devices typically include protection against brief high-voltage spikes, but don't protect against more moderate surges that last longer and are potentially more damaging.) Voltage is regulated between 105V and 135V: whatever the voltage of the incoming AC, the output is 120V. And with up to 1500W on tap, there isn't the current limiting that was characteristic of the original P300. Noise between 100kHz and 2MHz is reduced in all modes by more than 80dB. Like earlier Power Plants, the Premier has a fan, but the amp runs far more coolly than its predecessors; the fan isn't expected to come on unless there's considerable sustained current draw. In my situation, using the highly sensitive Avantgarde Uno Nano speakers, the fan stayed off most of the time; and when it was on, it was very quiet.