Any one measured the EMI/RFI attenuation performance of audiophile power conditioners?


I was looking for a very good/robust power conditioner which will clean up reliably very noisy/dirty power supply that I have in my aprtment. While looking for one I went through catlogs of AudioQuest, Shunyata Research, Synergestic Research etc. but no one published charts showing attenuation performance over frequency range like you get for EMI filters from Schurter or Schaffner etc. which are in the industry for EMI/EMC compliance.

Since audio is very subjective, but contrary to audio reproduction Power and EMI/RFI reduction is completely objective and can be clearly demonstrated via attenuation charts.

Hence I am asking if anyone has measured the actual performance of these audiophile power conditioners. I am not denying someone saying they hear improvement after using XYZ product, but since I am talking about power conditioning or EMI reduction it's as objective as it can be.

I am not at all surprised to see all the manufacturers not publishing the performance data, else it would be used in other industries and research fields where it's far more critical and have far more stringent requirements on the performance of conditioner/EMI filters. But I am shocked to see even products ranging above 5-10K are following the same practice of not publishing the results.

Please note I am not a measurement fanatic, but I know where I can chase the measurements and where I can rely on my hearing to gauge the difference.




To answer @Audio phool's question (sorry for a long reply - didn't have time to condense it):


QUESTION: "@vk_onfilter I saw the productline of your company which looks impressive & you seem to serve diverse industries including chip manufacturing, R&D centers etc. and you have provided the performance chart for your products. Besides you seem to have more than 40 years of experience in the field of EMI/RFI reduction/compliance. Is application of EMI/RFI filtering to audio any special than other industries you serve which allows one to not to specify the performance data? Can such practice will be acceptable if the same product was to used in other industries than in Audio?



The basic foundation of any technical product is a specification.  Engineering Bible starts with "In the beginning there was a specification" :)  In a number of ways a specification tells the designers of the products what a product should accomplish, in very specific terms (not "it should reduce noise a whole lot" but by how may dB at which frequency, and how it should be measured).  It tells the manufacturing group of the company that every single manufactured unit needs to meet or exceed very specific parameters (again, not just "sound good").  It is also a commitment that a supplier of a product gives to a customer - after all, the customer gives similar commitment to the supplier in a form of money.   Whenever you see a product that claims a whole lot but lacks that very specific commitment, it tells you quite a bit.  In the most benign case this would mean that a manufacturer has no idea what does this word "specification" actually mean - not a good notion for any product, especially a technical ones.  Anything else points to either knowing what that specification actually is and not being willing to present it to the customers; or thinking of a customer as an idiot who would buy anything "shiny" that is accompanied by flowery language and inflated price.  
In your own business, whatever it is, you likely buy and/or sell products and/or services.  Would you pay money in your business for something that has no "specification" of the sufficient type?  Would you feel right selling something where your customers have no idea what they are buying?

All our filters (of which AC EMI filters is just only one segment) have specification - sufficient to those in the industry who are in a need of noise reduction.  If we didn't have specifications and didn't stand behind it, truly, very few companies would even consider working with us.  From our perspective there isn't a difference between an EMI filter for a R&D center in a major university and the one for home audio - the only difference is so-call leakage current requirements to comply with the safety regulations - UL1283, UL/IEC 60939 (all our AC EMI filters are safety-certified by an independent accredited laboratory).  We have two basic kinds - industrial type, and hospital/medical/residential grade - grouped by the leakage current limits.

The sole purpose of a filter is to block to the best of its abilities incoming electrical noise and not affect in any adverse way the power itself.  Anything else is not a filter's job.  I believe it would be a mistake and an unreasonable expectation that somehow a filter (or a power conditioner) will improve sound quality, short of reducing incoming electrical noise.  Whatever quality problems you may be experiencing, don't start by adding a filter, unless all you need to reduce is noise.  Now, a poorly-designed filter/conditioner can add plenty of problems by itself, including intermodulation distortion, clipping, and so on - this is where a professional-grade product works, and the "shiny" ones may or may not.  

I do hear time to time from our customers in audio market that our filter either improved sound quality, or it didn't.  I would LOVE to know which specific parameters were affected - if only we knew it, the sky is the limit for the future improvements.  Studying for my MSEE specializing in audio I went through a good number of courses such as psychoacoustics, medical aspects of hearing, and alike.  I remember how at the conclusion of our course on Acoustics (a very demanding course because it is half-analytical and half-empirical) our professor said to the class "Now you know all that a man knows about sound, but only God knows what a man wants to hear" - that's sums it up.  I fully respect a huge subjectivity aspect of listening; I am also cognizant that if one buys an expensive "shiny" piece of equipment, one's brain works overtime to convince itself that it now sounds better for sure.

So, to conclude way-too-long of an essay, no, there is no difference for us in the filter design nor in requirements for the detailed specification for audio and for industrial or R&D market, short of safety regulations.

@tonywinga I am in the market searching for a power conditioner. So having the specifications and performance data will help me compare the options I have and make an informed decision.

I agree that speaker manufacturers do mot provide the data of individual drivers or electronics manufacturers do not provide info on the noise reduction incorporated. But for speaker manufacturer providing the specification of the entire speaker is more important than the individual one, hence specification of sensitivity, impedance & (in many cases) frequency response & in case of the electronics, they do provide the specification pertaining to the function of their product, e.g. if it's a pre-amp then they provide the gain & S/N ratio, impedances etc. Noise reduction is part of design which will mean how careful designer is to eliminate noises. Since thats not the primary function of that electronic they can skip on specifying how much reduction is achived through designing.

But in case of power conditioner it's main function is to reduce the EMI/Noise & manufacturers are omitting on specifying how well it's doing the job which it is supposed to do. Now imagine if Power amp, pre-amp or even DACs manufacturers stopped publishing all the specs? Isn't that problematic?

@vk_onfilter Thank you very much for the detailed reply. I appreciate your view on accepting both objectivity and subjectivity whereever applicable.

@deep_333 do read the response of vk_onfilter & let that sink in.


Reference page 14 of the Niagara 5000 Owners Manual which can be found online.  That seems to list some of the noise reduction specs that you are seeking perhaps.

@tonywinga thanks for pointing it out. I wonder why they kept it in user manual where no prospective buyer is likely to look into. Though these are not exactly what I am looking for but better than not having anything.


Want to point out that series mode power conditioners are essentially low pass filters that start working ~ 3 kHz. True for ZeroSurge and Furman with SMP while AFAIK, RFI filters usually start in the 10s of kilohertz. This is why I always recommend them for noise filtering efficiency.

Parallel filtration has a difficult time filtering out lower than that due to the limitations on caps across the hot and neutral. YMMV.

Also, keep your dirty power supplies (computer, cheap wall warts) out of the clean side of a power conditioner and use shielded power cables to ensure you don't suffer re-infection of noise after the power has been cleaned up.