Paul McGowan: High-End Survivor Page 3

McGowan: Exactly. It doesn't. It's like anything else that's connected through a resistance, in that some voltage is generated [across that resistance]. If that's the point where you're shunting off these harmonics and the other things you don't want, then they will actually reappear on that ground point. And if those harmonics are going up and down in time with the music, which will happen as the power amp draws current from the wall to the music, then you get a funny kind of modulation that contributes to the way things sound, a tinny quality or a glassy glare.

This is only a guess. But now that we're a bit more sensitive to this type of audible distortion, I can sit down to a system and pretty much hear the glare, because whether it's on a voice or on an instrument, that glare tends to ride with the music. When we run that same system through a perfect voltage source, a regulated AC source, that glare is gone.

Atkinson: So when you regenerate the AC supply with a Power Plant, the components you plug into it are now being fed from a perfect voltage source. Whatever their current demands are, they're still being fed with a constant AC voltage.

McGowan: That's correct. The Power Plant is essentially a power amplifier being fed by a DSP-based sinewave generator. And if the device that's being driven by the Power Plant demands current in an irregular fashion, what will happen is that, because the Power Plant is an amplifier with negative feedback, it is able to compensate for that asymmetrical or nonsinusoidal current demand. The Power Plant's power supply is able to pump more current to meet those demands. Whereas, if you plug the device directly into the wall socket, depending on the resistance inside of the line, you get a modulation effect due to the current demands.

Atkinson: And that modulation ends up riding on the signal ground in your amplifier or preamp.

McGowan: We can see that on a 'scope. If you tie a fairly high-value resistor on one side to the device's signal ground and the other side to a [true] earth ground, you can actually see the modulation.

Atkinson: So what are the downsides of AC power-supply regeneration?

McGowan: It's not very efficient. At the moment, that's one of the major drawbacks. And it's rather expensive compared to a power-line filter or whatever.

Atkinson: Traditional power-line conditioners can get rid of radio-frequency rubbish and sudden spikes on the line, but I assume they are less good at removing this audio-band harmonic content?

McGowan: Right. We've tested pretty much everything on the market that we've been able to get out our hands on. No filter that we have seen is able to get rid of anything below the ninth harmonic, and, as I said earlier, the majority of the harmonic content is below that. And they certainly can't get rid of the flat-topping of the sinewave, because that would require you to actually add voltage and current in an appropriate manner. No filter, no balanced transformer, can do that. Balanced transformers are better than PLCs in that they have a prayer of eliminating some of the lower harmonics by virtue of common-mode rejection—if the harmonics are generated in a common-mode fashion. But they can't fix the flat-topping.

Atkinson: And that flat top—that's what comes off the transformer on the pole.

McGowan: That's exactly right. You're trapped and doomed. We've seen some very bad instances . . . in airports, for example. I have never witnessed a 60-cycle AC waveform that's below about 2.5% distortion.

One thing I'd like people to understand is that PS Audio did not invent this technology. Power supplies using sinewave regeneration have been around in laboratories and scientific environments for what, 30 years? We have a friend, Doug Goldberg, who works at North American Grumman. He has in his lab huge, hundred-thousand-dollar Power Plants, if you will. We were just the people who adapted it to the hi-fi and video industries.

Atkinson: Video?

McGowan: This was brought up in a review in another magazine. When we went home and tried it, by God, the reviewer was right!

In the movie Contact, when Jodie Foster is looking up at the evening sky, even when you view the DVD on a ProScan or another very good monitor, as you look at the sky, it starts out very black, but as it goes down toward the horizon it's amorphous, it doesn't really have a shape to it. When you plug the television monitor into the Power Plant, all of a sudden what you see is that while it starts out as a very black sky, it goes down through different shades of blue into dark purple and fades out into the horizon.

TVs are very susceptible to voltage modulation, and a big TV sucks a lot of juice out of the wall. Depending on how much resistance is in the 12-gauge line back to your circuit breaker, when the [electron guns] fire they draw current, and depending on how well they're regulated or not regulated, this is going to modulate the voltage to some extent. And that will make the colors dimmer. But if you feed a television with a voltage-regulated AC source such as the Power Plant, then the television is able to deliver exactly as much current to the gun as it needs. The difference is pretty visible.

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