Inner Workings: Inside a Power Conditioner

Surge protectors - or, more precisely, transient-voltage surge suppressors - are becoming a necessary part of any home theater. Although many basic strip-style surge suppressors offer some protection against destructive power surges, spikes, and even indirect lightning strikes, A/V enthusiasts are increasingly turning to "power conditioners" that not only protect against surges but also clean up noisy AC power, which if bad enough can degrade audio and video performance.

Belkin's top-of-the-line Power Console PF60 ($600) is a good example. Like many surge protectors, it uses metal-oxide varistors (MOVs), plus a thermal circuit breaker, to deal with dangerous spikes along the AC power line. MOVs between the power and ground lines divert, or shunt, surges of excess voltage to the ground, cutting power to your gear when the input voltage reaches a dangerous level, then restoring it when the voltage returns to a safe level. For power conditioning, the PF60 uses dedicated filters to eliminate electromagnetic (EM) and radio-frequency (RF) interference and isolate the various digital, high-, and low-current A/V components so the noise they create doesn't bleed from one to another.

The PF60's back panel has 12 outlets for plugging in your A/V components and eight coaxial inputs/outputs for connecting cable boxes, satellite receivers, and external antennas or TV tuners. Protection is also provided for phone lines via one incoming RJ11 phone jack and two outgoing lines and for home networks via in/out RJ45 Ethernet jacks. Above the heavy-duty power cord is a 15-amp circuit breaker that pops when loads exceed either 15 amps or 1,800 watts.

Each of the six outlet banks (two outlets per bank) is labeled for certain types of components. Banks 1 and 2 are for digital gear such as DVD players, while Bank 3 handles video components such as TVs and VCRs. Banks 4 and 5 are for audio gear such as preamps, and Bank 6 is for high-power amps and receivers.

The banks have isolated filters designed to deal with specific types of noise and to keep noise from one type of device from contaminating other banks. Banks 1 and 2, for instance, have two-stage toroidal choke coils that clean and condition power going to digital components and reduce the digital noise they generate back down their power cords, while Bank 3 has a single large toroidal choke for video noise. Each bank can be set for switched or unswitched (always-on) operation, and you can set the switched outlets for 5-, 10-, or 15-second delays, which help prevent loud pops from going through speakers when components kick in after the amplifier's already on. The main power cord has a large ferrite-core band that guards against interference generated by other devices inside the house, such as fluorescent lights.

Next to the outlet banks is the console's main circuit board, with two Microchip PIC processors that act as the unit's brains. Above and to the right of the board are two power transformers and a pair of commode-mode chokes - small cylinders wrapped in wire that provide additional protection against EM and RF interference on the AC line. An additional series of MOVs and thermal fuses provides three-stage protection against spikes on the main AC line.

Similar devices may add more power conditioning, such as voltage regulation, AC regeneration, or uninterruptible power supplies.

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