Power grid interference: What does it look like measured with different tools?

[DavidPiska]

If you're interested to see what power grid interference looks like, take a look at the videos below, or a comprehensive article about it here: https://rdacoustic.cz/en/blog/2021/04/30/f4sx-audio-power-filter/ (explains in detail what I did here and includes background info + why is it important in audio). A few months ago, I posted measurements of power grid interference using a spectrum analyzer. Other measuring techniques include EMI line meters and oscilloscopes.

Measurements using an EMI meter:

Using an oscilloscope:

A closer look:

And using a spectrum analyzer:

This is Europe. I would be interested to see what it looks like on other continents if anybody has any measurements or experience.

 

[Addicted to hifi]

Very interesting.

 

[Peguinpower]

This guy posted his own version of AC line noise test, and says he didnt see a difference in the actual output of a Topping D90 DAC. Im not impressed by this fella, the test if very narrowly focused, but its just as valid as your experiment.

 

[Alrainbow]

Without a reference how does this matter, ?
The filter shown is most likly loading the freq if the line noise centered on the measuring device shown . What other noise is there ? A person like ralph can explain better . Also if you cant see any change on a cheap toppings dac then it matters even less. Ps i own a toppings d90se lol

 

[Republicoftexas69]

One cannot take anything Amir at ASR posts as serious. Science left his forum long ago. His tests are limited in product scope and test detail.

 

[MaxwellsEq]

I would expect any competent electronic designer should be able to design solutions that reject electrical line noise. Perhaps some domestic audio kit has inadequate mains noise rejection, but professional studio kit would be thrown out if it couldn't handle mains-bourne noise properly.

 

[Alrainbow]

Amir has his own thoughts and is done very well. Now conclusions is of course to each there own
not all noise effects over all sound much be Measured. I’ve read many of his detailed articles he is spot on in what he does. It’s the effects that things get off the road for some.
I own the toppings it’s a very good dac in many ways
Now it’s no Lampi H or many others above it’s level of musicality
it’s a twinkle high detail sound. but if we dial it in to make it have more body it’s pretty good.
his view in sound I don’t always agree but no one does here.

 

[Alrainbow]

I would expect any competent electronic designer should be able to design solutions that reject electrical line noise. Perhaps some domestic audio kit has inadequate mains noise rejection, but professional studio kit would be thrown out if it couldn't handle mains-bourne noise properly.

Regulators remove noise but also add there own st times
Line noise reduction can be needed but most don’t
where line noise matters is any device that has a
Large gain phono pre for one
A pre amp not so much and an amp
Less still.
a dac is very complex and has many of its noises to deal with from all directions.
just sayhg

 

[MaxwellsEq]

A mixing desk has high gain microphone stages dealing with low signals. Each channel has sequences of gain, attenuation, switching, gain, attenuation, switching etc.

Each stage has optimised power noise rejection.

If mixing desks were susceptible to mains-bourne noise, all recordings and broadcasts would have mains-bourne noise in them. But they don't. So this proves good designers can deal with power grid interference.

 

[Kingrex]

If you know me, I have been digging around the idea of battery inverter power. Most all these inverters operate wirh a 20KHz sine wave generator. As well as a GHz dc to dc voltage booster on high frequency inverters. All the people using these inverters use a Puritan 156 on the load of the inverter. They say it alters the sound in a positive way.

I watched ASR do a study of the Puritan. Sure enough, the puritan did an excellent job of filtering the 20KHz noise. But using the puritan had 0 impact with the simplistic study Amir did on the output of 2 devices. As in, test 1 direct to wall and test 2 from the puritan show the same output signal from the audio device no matter what it's plugged into it.

This makes me wonder, what noise is coming from the inverter the Puritan is filtering that does get through the power supply of a piece of equipment.

Is Amir a failed engineer that does not know what tools to measure with? What is he missing? Why do people find filters to help. Where are they impacting the AC.