Powerline Accessory Reviews

To ensure that no electronic nasties reach the equipment connected to it, and that the Power Plant itself is protected from damage, PS Audio has taken a comprehensive approach. It starts on the input side with a megahertz-range filter to deal with any radio-frequency energy riding on the AC. Catastrophic protection is provided in the output stage by opto-isolators placed across the emitter resistors. When a predetermined voltage drop develops across the emitter resistor, the opto-isolator sends a signal to the Power Plant's microprocessor, which shuts down the power activation relay.

In the driver stage, there's a circuit that limits turn-on current. Yet another circuit monitors the current delivery on an ongoing basis, and the ubiquitous microprocessor calculates the average RMS current, displaying the result on the front-panel display. Delivery of 10% over rated power alerts the microprocessor to shut down the Power Plant's operation. I inadvertently tested the P300's protection modes when I plugged a video projector into it. The projector evidently draws considerably more than the rated 300W; the Power Plant shut down immediately, with no damage to either component.

The P300 is intended for use with source components, preamplifiers, and low-wattage amplifiers, the recommended maximum load being 200W. PS Audio has in the works three higher-powered Power Plant models (the P600, P1200, and P2000, the model numbers indicating output in watts) for use with amplifiers and video projectors. There are also forthcoming audio amplifiers based on the Power Plant's basic design.

The P300's attractive, somewhat unusual industrial design—narrow and deep, with curved side panels—allows it to be placed side-by-side with the matching PA300 audio amplifier (footnote 3). The back sports an IEC AC input jack, four hospital-grade AC receptacles, a master on/off switch, a grounding post, and CATV in/out F-connectors to provide protection from lightning to video equipment. It's possible to disconnect the receptacles' AC ground wires inside the Power Plant (a simple process, involving a plug-in connector, but you have to get the instructions from the factory) and connect a separate external ground to the grounding post. This prevents noise that might be present on the AC ground from entering the system. If you decide to disconnect the AC ground, safety requires that you provide an alternate ground path through the grounding post. (See Jonathan Scull's "Fine Tunes" column in the August 1999 issue.) I don't have convenient access to a separate ground, so I left the AC ground alone.

On the front panel are the Power button (which switches the AC outlets), a numerical display, a Mode button that toggles the display between showing output wattage and output frequency, and two buttons that allow varying output frequency from 50Hz to 120Hz. PS Audio's term for variable AC frequency is "Power Factor," about which I'll have more to say anon. The front panel also features a prominent "PS" logo, illuminated in bright blue. It's nicely done, but if you do a lot of your listening in the dark, you might find it and the illuminated numerical display distracting enough to want to orient the Power Plant so it faces away from the listening area. (I did.)

The Power Plant's build quality is obviously high level, with a chassis designed and built by Neal Feay, a company that does work for the likes of Theta, Conrad-Johnson, BAT, and Sonic Frontiers. The first sample I received had a fairly high level of mechanical hum, apparently the result of some rougher-than-usual handling in shipping. PS Audio dispatched a second sample, which was much quieter.

Music to my ears
Most audiophiles have encountered the problem of evaluating a piece of equipment that, sure enough, changes the sound of the system, but doesn't necessarily represent an improvement. Or that of having the sound be better in some ways than in others (eg, smoother treble, weak bass extension. When this happens, deciding whether the component is better overall involves weighing the pluses and minuses—a difficult process.

In the case of the P300 Power Plant, I didn't have to face this sort of dilemma. With preamplifier and digital source components plugged into the P300, the sound was not merely different, but in every way relevant to the listening experience, significantly better. This was true whether the comparison was with raw AC from a dedicated line or either of two more traditional PLCs: the Tice Series II Power Block and the latest Chang Lightspeed CLS 9600ISO. The Tice changed the sound too much in the direction of softness, and dynamics were reduced. The Chang was better than the Tice, and left dynamics alone, but the improvement over raw AC was not nearly as great as with the Power Plant. The benefits of the Power Plant were such that it took a real effort of will for me to take it out of the system to make the comparisons.

One might expect that the most obvious improvement would be in noise level, but this was not the case. Noise was lower, but the magnitude of the change was quite small. (Noise is not normally a problem in my system.) The most striking effects of the Power Plant were in the upper midrange and highs, which were stripped of much of the "electronic" overlay that I had thought was an unavoidable result of the distortions inherent in the process of sound reproduction or was part of the recordings themselves.

Recordings old and new sounded fresher, more immediate—more like real music, less like reproductions. The highs became more pristine and extended, with no hint of euphonic rolloff. There was greater clarity throughout the bass region, too, with string bass, bass guitar, timpani, and bass drum better defined. Resolution was enhanced; I was able to hear subtle details that had previously been merely hinted at or even obscured. Instrumental and vocal timbres became more distinctive, and spatial definition was enhanced, the soundstage expanding laterally and in depth. This increase in resolution was not at the cost of reduced smoothness or musicality. Although I could hear more of the recording artifacts, such as added reverb, they were not distracting; music continued to hold center stage.

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Footnote 3: Normally, an amplifier like the PA300, whose output is 150Wpc, would require a Power Plant with an output of at least 600W, but each of the forthcoming PS Audio amplifiers will have an isolated voltage gain stage, with special AC inputs to drive just this stage. Although this leaves the current stage with raw AC, the benefits of the Power Plant are said to be most evident at the voltage stage.