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Hi-Fi and Pro Audio

EMI Filters for Hi-Fi Audio

"Just a quick note to say thank you for the noise filter.  The filter has proven to be completely effective in eliminating any of the issues I was experiencing. So effective in fact that I cannot even hear the amplifiers’ toroidals in operation at idle or under any listening levels with my ear on the amps’ case. The amps’ noise floor is now utterly silent, and it seems to be running slightly cooler as well.  Thanks again for the excellent filter" (R.B., Canada)

"I think you build an excellent product that the audiophile industry ought to know about" K.F

With the substantial effort and budget put into achieving superb sound quality, it would be a pity if EMI from power lines and ground ruin it all by adding its "creative content" to the sound.


OnFILTER' CleanSweep® AC EMI filters were designed to deal with industrial noise that exceeds anything that one could encounter at home or in a studio, often by several orders of magnitude.  CleanSweep® filters are capable of attenuating high-frequency artifacts on power lines and ground from tens of volts easily found at the factories down to just a few millivolts, enabling operation of super-sensitive semiconductor equipment. 

EMI found in home or in a studio environment is easy for CleanSweep® filters.  The filters offer noise suppression in both differential (between Live and Neutral) and common (Live/Neutral to Ground) modes and, uniquely, in ground, completely isolating your equipment from EMI on the mains.

Importantly, CleanSweep® filters are not transformer-based.  Transformers in power line present high output impedance for the load, i.e. your amplifier.  This leads to variations of supply voltage with current peaks and, as a result, to intermodulation distortions, reduction of dynamic range, and other artifacts.  Transformless design allows for full dynamic range without added distortion.


A common myth about transformers is that they excel in suppressing common mode EMI.  Not true - read independent review in EDN Magazine (covers our MSN15 EMI Adapter and CleanSweep® AC EMI filter).

Read this Application Note for more details and guidance on filter's installation.

"We installed the filters, did some initial testing, and then did some more extended config and testing.  So far we have been rock solid on amp performance, and according to the audio install guys, it seems like we are both getting better raw performance as well as have had the system running without issues longer than it ever ran previously. "

Church Sound Installation, Chicago

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...just installed the filter and i went from 1000 mv to 150 mv of noise using a emi broadband meter, noticed tighter bass response and extended high frequencies. There was also an increase in dynamic range. Much appreciated!   S.A.

"I tried a number of power conditioners, filters and EMI/RFI reducing products marketed to audiophiles. None of them had much effect reducing EMI/RFI. The only devices that performed as promised and significantly reduced EMI were CleanSweep filters made by OnFilter."

Note on Installation

CleanSweep filters uniquely provide filtering in ground, therefore it is critical that you power all your equipment via the filter to avoid EMI on ground sneaking in via some unfiltered component.  If you need more than one outlet, you can use any quality power strip connected to the filter's output - no additional filtering in it please, just assure that it has adequate wire gage of at least AWG12.

Performance of CleanSweep AC EMI filter vs. transformer (read review)

CleanSweep AC EMI filters outperform regular EMI filters in real-life applicatons

CleanSweep® AC EMI filters are not the same as the conventional filters you can find elsewhere. Regular filters are designed to perform only in an artificial laboratory conditions with 50 Ohms power termination.  When plugged into actual power mains, they may amplify noise - see above.  CleanSweep® EMI filters are designed for real-life applications (they perform well in the lab too).

Application Notes

CleanSweep® AC EMI Filters in Audio Applications

CleanSweep® Filters in Surge Protection

OnFILTER Advantage: Summary of CleanSweep® AC EMI Filter Technology

CleanSweep® AC EMI Filters and UPS

Review: Tool Measures Power-Line EMI

Technical Articles
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