PS Audio Ultimate Outlet AC conditioner
And it works. Almost every piece of equipment seems to benefit from getting its AC from a Power Plant—even high-end preamplifiers with sophisticated power supplies (see my review in Stereophile, Vol.22 No.12 and John Atkinson's Follow-Up in Vol.23 No.5). The MultiWave option extends the functioning of the Power Plant by including complex waveforms that have the potential to drive audio equipment power supplies more effectively than standard 60Hz AC (see Vol.23 No.12).
Although the Power Plant is a wonderful product, it's not without some drawbacks. First of all, there is cost: the P300 with MultiWave and fan is $1245—more than reasonable, considering the technology and the sonic benefits, but still too much for many audiophiles. With the P600, you're looking at $2395, and the P1200 will set you back $3999—again, not excessive, considering the fact that you're getting a beefy amplifier for your money, but not a casual purchase for most people. They're big, heavy, and—at least the P300—tend to produce a fair amount of heat.
The P300 will run source components and most preamplifiers, but it does not have enough output for anything but very-low-powered amplifiers. As a rule, an class-AB amplifier draws twice the power that it delivers, so a 250Wpc stereo amplifier would need up to 1000W, and that would require the P1200, which weighs 150 lbs and is almost 3' long! And, of course, there's the associated cost of electricity just to run the Power Plant, the wattage draw being similarly up to twice the rated output; ie, 600W for the P300, 1200W for the P600, and a whopping 2400W for the P1200. (However, as the Power Plants run in class-AB, not class-A, at least the idle current is relatively low.) The Ultimate Outlet was designed to provide power-line conditioning at a lower price than the Power Plant devices, and, when used in conjunction with a Power Plant, to produce further reduction of noise and electromagnetic interference (EMI).
The Ultimate Outlet (UO) is a smallish metal box with an IEC input connector at one end and a duplex AC socket at the other. Inside the box is a type of transformer called a balun. Prior to my acquaintance with the UO, the only balun that I was familiar with was the type used to match a 75 ohm coaxial antenna cable to the 300 ohm antenna terminals of a TV set. In fact, balun transformers are used widely in RF/microwave transmission applications, but, according to PS Audio's Paul McGowan, the UO represents the first use of a balun in an AC power context.
A balun is a fairly simple device, consisting of a donut of iron with wire wrapped around each half of the donut. The balun used in the UO has the wire connected directly from input to output, so that it's not like an isolation transformer. The claimed advantages of the balun-based over the series/parallel filter or isolation-transformer-based approaches to power-line conditioning are: a) cancellation of noise at a much wider range of frequencies, b) reduction of differential as well as common-mode noise, and c) no limitation of power.