Measuring line noise and power conditioners

Sorry for all the posts, but this thread is just a wealth of misinformation. Take his 1/2 truth from onfilter.com who is trying to do what? Sell you filters

Some points:  Most people add filters to their designed products not to reduce noise getting into them, but to reduce noise getting out of them to pass EMI. his part they got right.

The "standard" line impedance used for testing varies from 0.1 ohm to 0.4ohms, at low frequencies, which is not where EMI is tested. IEC60669 defines common line impedance for 230V as 0.2ohms and 400uH. North American standards for 120V are typically 0.2-0.4ohm, and 100uH - 400uh.  FCC conducted emissions testing begins at 150KHz. At 150KHz, 400uH = 60 ohms, at 100uH = 15ohms. That transformer outside your house is not presenting a 0.1ohm source impedance at 150KHz.  Now I am not complaining that OnFilter products don't do anything, likely they do, but they aren't being very honest with the information they are presenting. Now there are likely things in your house, i.e. motors, dimmers, etc. that because they are close have more impedance, but even 30 feet of Romex is 3-4 ohms at 150Khz.

The 50 ohms used in EMC measurement is more of a parasitic impedance, and unavoidable due to the input impedance of test equipment, and the passive setup. Technically in EMI/EMC measurement, the equipment is fully isolated from the AC and the measurement is volts.

Conventional filters will do little in actual power lines or may even amplify EMI - it is in their own specification (that is, for those manufacturers who bother to publish such specification). For a brief explanation please see this link: https://www.onfilter.com/real-life-filtering    In short, regular filters are designed to perform at 50 Ohms termination (in and out) for EMC Compliance - CE and FCC. I personally haven't met a power line with 50 Ohms impedance. In real-life applications a better impedance ratio is 1/100 or 0.1/100 (not a critical difference in reality) where 1 or 0.1 is output impedance of AC power and 100 is rough number for a load, i.e. your amplifier. It is imprecise but much more realistic than 50/50 Ohms. Since a filter is a combination of inductors and capacitors, when designed with one goal in mind to work in a 50/50 Ohms environment, this is where it "tuned" to. In actual use it either does nothing or amplifies noise. Our company (tooting my own horn here) designed filters for actual installations that we provide to the factories around the world, NASA, governments, hospitals, etc. - they are impedance-independent and essentially kill emissions anywhere they are plugged in -

While I don't agree with caycol in totality, a good portion of what he is stating is true at least for audio. In a well designed product, high frequency external RF noise is much easier to get rid of than low frequency noise, i.e. in the audio band on power lines, and guess what, low inductance, low capacitance AC cords are not going to help the situation, though consistency of the chassis ground reference between equipment can be critical for low noise.

High frequency RF as measured by these EMI toys does not represent well the much harder to filter frequencies on the AC line that are either in the audio band and/or close it and can sub-modulate down into the audio band.

Where the problems come in is with low level, high impedance signals such as interconnects, whose signal path may include the chassis ground due to intentional (or unintentional) capacitance between the signal ground and chassis ground (usually intentional).

piaudiol, most of the papers you linked have nothing to do with the topic specifically, which really doesn't address the effectiveness of line conditioners either where it matters, nor do they really refute caykol, though they do introduce topics such as ground loops, and hum, that my have nothing to do with EMI filtering at all.

This keeps being repeated as "factual", when it never has been. The output of a rectifier includes DC and high frequency components. Simple transfer function analysis. The more of those high frequencies you eliminate, the greater the ratio of DC to AC. Those high frequencies can extend dynamic range of the amplifier by providing a higher minimum voltage on the capacitors, but they will never contribute to lower noise. They will always contribute to more noise.

The circuits in the amplifier or other equipment may prefer the higher voltage being designed that way (bias values, etc), but the noise is never going to be less.

For emphasis, this is a simple one way transfer function, it is not loop analysis where high bandwidth can be used to cancel noise.

The spectral composition of that current draw therefore includes frequencies that are much higher than 60 Hz, and filtering those higher frequencies out will tend to adversely affect perceived dynamics and other sonic characteristics. Which is no doubt a major reason why many audiophiles prefer to plug power amps directly into the wall outlet.
In fact Ralph (Atmasphere) has stated in past threads that in many cases these desirable frequency components can range up to several tens of kHz, and I have no reason to doubt that. And if I recall correctly Shunyata has a paper in which measurements are presented supporting that conclusion.

Generally people don't think of frequencies in the audio band (<=20KHz) as EMI, but as line harmonics. 20Khz has a wavelength of 9 miles (15km), so you need a pretty big wire for a good antenna. These EMI toys don't measure harmonics. You need a good power meter for that. They of course don't give you the spectrum either.

Well I am not Paul's biggest fan, or the biggest fan of expensive power cords (I think there are better ways to address the purported improvements), the Niagara 1200 is an intelligently designed product. Electrical noise can be insidious and finds its way in through many avenues and even when the noise is not audio frequencies, they can be converted to audio frequencies. The Niagara appears to address many of those paths.

mammothguy5434 posts06-13-2020 1:53pmI got an Audioquest Niagara 1200 ..
What I can say is that my system sounds far more dynamic and clean, than ever before. The concept and the product work exceptionally well.
My ears told me so. 'Nuff said...

I understood that you meant AC filtering. I am calling into question the need for the high frequency components on the AC line, other than to maintain the supply rail voltage post rectification. I don't agree that filtering out those frequencies will have an adverse impact on dynamics, other than as it would impact the rail voltage after rectification. If anything, an amplifier with adequate capacitance, designed to reduce as much of those high frequency components as possible (hence why chokes, etc. are often added to to the circuit to reduce high frequencies) would have lower noise and distortion and be able to more accurately portray dynamics.

The spectral composition of that current draw therefore includes frequencies that are much higher than 60 Hz, and filtering those higher frequencies out will tend to adversely affect perceived dynamics and other sonic characteristics. Which is no doubt a major reason why many audiophiles prefer to plug power amps directly into the wall outlet.

So what was this @geoffkait , lazy reading, excessive trolling of every post I make, or did you not understand what I posted.

1) High frequency RF as measured by these EMI toys does not represent well the much harder to filter frequencies on the AC line that are EITHER IN THE AUDIO BAND AND/OR CLOSE (to) IT and can sub-modulate down into the audio band.

Here I quite clearly state, I bolded it for you, what I wrote, that again clearly states AUDIO frequencies and frequencies CLOSE TO AUDIO that can sub-modulate down to the audio band.

>>>>Sub-modulate down to the audio band? Are you high? Radio Waves are not even in the same domain as acoustic waves. How can MHz or GHz electromagnetic waves submodulate down to the acoustic band? It almost sounds like you actually think the acoustic waveform is traveling through the wires and cables.

Now, perhaps a bit of an education to fill some missing holes in your knowledge.

1. Rectification acts as a modulation function. Rectifying AC and you get a DC component as a modulation product. Rectify electrical AM radio signals and what do you get? ... Audio frequencies. Why can a dimmer be so problematic? First you get the 120Hz ripples, but then on top of that, you get high frequency ringing which rides on top of the AC --- gets rectified .. still following me? ... and guess what, you get 120Hz bursts getting past low frequency filters, plus harmonics. Isn't noise grand?
2. What happens when you sample an FM radio signal at 100MHz with a 100MHz ADC? ... you get audio frequencies. Wow huh! What happens when the noise from a 100KHz frequency switching power supply say gets into a 96Khz DAC clock, hmmm... you get 4KHz. Now most up-sample, so it would be high frequency harmonics of the 100Khz impacting the say 768KHz 8x oversampled clock of an R2R DAC, so you have to be concerned with high frequency noise up near that frequency. With a sigma-delta DAC, the harmonic products are more complex.
   

When you say the EMOTIVA did not work, do you mean it did not reduce the measured value much?

danvignau, .... didn't realize you were putting out fly paper did you? :-)