In the 2000s home theater owners were investing heavily in Blu-ray, digital receivers,and plasma TVs to take advantage of Lucasfilm THX, Dolby Digital, and DTS surround. In this less-green time it was a status symbol to have a bank of power amplifiers and a complete home theater library of locally stored content. Today, the shift towards cloud-based content has moved to smart TVs with soundbars. The result is less space for a dedicated surge supressor yet protecting AV equipment from noise is just as important as before.

BELKIN was founded in southern California in 1983 by Chet Pipkin in his parent's garage. A great personal story as today Belkin is now a worldwide company and owns both Cisco and Linksys. In the early 2000s they released line conditioners for the consumer AV market. These were stylish units with the Belkin stamp of quality to fill a necessary home theater niche. Models were the PF-30, 40, and 60. In a mysterious move around 2010 Bekin decided to discontinue the entire line, much to the disappointment of the AV community. It was a shame because these were affordable quality units with unique styling and elegant displays instead of the rough industrial look of other brands. A competitor Monster Cable made sylish units that were well regarded but were also discontinued around the same time.

In 2006 I bought a new silver PF30 (AP20800-10) and a black (AP20800-08). The silver version is dated 11/2002 and the black one 5/2005. The silver design is very pleasing I wonder why the later black version changed to plain labeling. Were there other changes? See below.

For AC line filtering its important to understand the Stage 1 filter which has been around for decades and used extensively worldwide. The purpose of a Stage 1 filter is to block EMI/RFI above 60Hz almost like a speaker crossover. However only so much filtering can be added without causing insertion loss (voltage drop) and distorting the 60HZ sine wave. UL (Underwriters Laboratory) certifies this simple filter on US power grids which means that Stage 1 filters are pretty much the norm in line conditioners even high end models.

- Special "X" and "Y" type capacitors are used. One X cap goes between the rails (called Differential mode) while two Y caps go from rail to ground (called Common mode). An X type burns through when blown while the Y keeps drawing current when blown to maintain grounding. These caps filter out EMI/RFI.

- Toroidal chokes and wire-wound coils are used inline with each rail to filter out high frequencies.

- A MOV is sometimes used inline with each rail at the outputs. These increase resistance as voltage rises and clamp down on spikes.

BELOW This silver PF30 had four coaxial jacks for cable/satellite in addition to ethernet and telephone line protection. The black unit has no ethernet/phone feature and only two coaxial jacks. The black unit has red LEDs on the 'always on' outlets.

BELOW The silver PF30 layout is clean and functional. It appears to use Stage 1 filters without Y caps. Note the fuses on the upper left which are the protection for the ethernet lines. The small silver components between the orange MOVs are thermal fuses.

Belkin promotes its "Purefilter" circuit as a key feature and puts a light on the front panel to show the function working. The manual says "The multiphase PureFilter Circuitry provides true isolation between audio, video, and high-current components". Euphemisms aside its simply a name given to the three individual filter banks. The manual says there is overvoltage protection that disconnects and reconnects when necessary. I suspect this refers to the MOVS.

BELOW The black PF30 has more parts on the board despite no ethernet and RJ45 protection the black . This includes a larger PIC16F flash microprocessor and three white sandcast 5W power resistors to replace the 2W versions used on the earlier model. Carli capacitors are the same but the MOVS and thermal fuses are different brands. The board is stamped PF-30D_V1.2 while the older model has no version number.

I noticed something odd however. With the top open and the unit switched off the three white power resistors in the center were very warm. The audio outlets on the back are listed as "always on" but heat coming off worried me the unit was wasting power even when off. So I ran a meter on the unit and the current draw calculated out to only $.17 a year.

So do line conditioners serve a purpose? Absolutely! The amount of EMI/RFI on modern power grids is significant. Allowing it to pass into expensive TVs and AV systems is very risky and irresponsible to ignore in my opinion. Creating a safe harbor for your equipment should be a priority. However, marketing AV filters to the general public is tricky. Despite the filters' effectiveness in many cases they don't produce an audible result. The result is that the mainstream scoffed at their effectiveness while some considered them worthless. I find this humourous considering how much people spend on AV products with little or no benefit yet find it hard to believe that filtering EMI/RFI is a good thing.

COMMENT: One criticism is when companies use cute names like "Power Technology" or "Pure Filtering" to describe their filter circuits inside. This is a poor advertising choice because people who understand RFI concepts are the ones most likely to buy quality surge supressors. So instead of dumbing down the concepts why not openly state the components used inside and explain the schematic used? This is the only way for the informed consumer to compare these workhorse products and their effectiveness.