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 and filled 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 unit that were well regarded but were also discontinued around the same time.
In 2006 I bought a new PF40 mailorder from 6th Street Photo. With PURE AV stamped in the top cover and on the front it had a high-tech look. The front AC outlet had a neat little silver cover.
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STAGE 1 FILTER
When it comes to line filtering its important to understand the Stage 1 filter which has been around for decades and is 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. This 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 (open) 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.
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This unit has protection on 6 coaxial jacks for cable/satellite in addition to ethernet and telephone line protection. Two of the switched outlets are high current versions specifically for amplifers.
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BELOW: The PF40 layout is clean and functional. AC from the wall passes to the power supply board and transformers on the left. Clean AC then passes to the 2nd board where four banks of Stage 1 filters with MOVs travel to the rear outlets. Large ferrite beads are used on each outlet.
Belkin promoted its "Purefilter" circuit as a key feature. The manual says "The multiphase PureFilter Circuitry provides true isolation
between audio, video, and high-current components". This term simply means there are individual filter banks.
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| A closeup reveals X2 caps, coils, and orange MOVs. The small silver components between the orange MOVs are thermal fuses. The use of multiple Stage 1 filters and attention to detail and layout is top notch in my opinion |
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CONCLUSION
The concepts of using chokes and capacitors to filter out line noise are decades old. I find it very puzzling that surge suppressor companies give cute names to their audio circuits than explain them in detail. By dumbing concepts down companies may have contributed to a perception that these products are snake oil, which is very far from the truth. Surge supressor manuals should describe in detail the circuit inside so the buyer can make comparisons between brands and models. Even today quality brands such as Furman and Panamax state the features of EMI/RFI noise filtering but don't explain how they accomplish it.
A look under the hood by the manufacturers would go a long way to build consumer confidence in what is unnecessarily mysterious.
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