Impact of AC Distortion & Noise on Audio Equipment

[IVX]

Oh, I forgot to mention one real and quite obvious effect of clean AC sine. AC line distortions are mostly a 3rd harmonic which looks like a cutting of sine peaks. Power amps PS takes the current from that peaks, and in case of THD = 10% your power amp rails could be about 10% lower vs clean sine powered. It may sounds like more punch, more controlled bass, more solid and so on.

 

[alek19000]

GREAT ! Save my money for good!!!!

 

[pma]

There have been a number of quite blatant logical fallacies in argument here, so much so I feel quite depressed about the entire exercise. People who are smart enough to know better are making some really poor arguments and blunders because they are blinkered in their desire to disprove yet another audiophool myth.

Exactly. Very well said.

 

[pma]

I don't have a tube amp.

I have a tube preamp. This is the impact of RC ripple current control (remote control that is transferred via mains as a superposition of impulse trains) to preamp noise. Measurable and quantifiable. Noise increased from 22uV to 28uV.

Normal

With ripple control

 

[H-713]

There is a clear logical fallacy of false syllogism occurring here.

The tests so far have been:

There is a claim that poor audio equipment can benefit,
Here is a poor bit of equipment,
It didn't benefit,
Therefore, there do not exist any examples of equipment that can benefit.
...
This is junk, and the sort of crap arguments I would expect from the audiophool community.

The other argument in this thread that has been rampant is that any equipment that is susceptible to issues from this is a bad design and should just be replaced rather than buying a power conditioner. This obviously doesn't make sense in all circumstances- sometimes there is very good reason to be using a piece of equipment despite (or even because of) its flaws.

It's talking around the problem rather than addressing it.

Perhaps a more useful demonstration would be to find some equipment that does have issues, then use it to demonstrate where power conditioners make sense and where they don't.

It falls under the same category as cables. They can matter, under some circumstances (1000 feet of CAT 5e used as speaker cable does have an audible and measurable impact over more sensible choices). Power conditioning can be needed under some circumstances, but obviously not always.

 

[amirm]

Oh, I forgot to mention one real and quite obvious effect of clean AC sine. AC line distortions are mostly a 3rd harmonic which looks like a cutting of sine peaks. Power amps PS takes the current from that peaks, and in case of THD = 10% your power amp rails could be about 10% lower vs clean sine powered. It may sounds like more punch, more controlled bass, more solid and so on.

Not really. Your power supply has reservoir capacitors. And is running at much lower voltages than mains. It also has feedback. So all this time everyone who doesn't have such devices has been losing bass, etc.? I don't think so.

What is going on with you all and these arguments?

 

[amirm]

Let me contribute with some facts. The thread name is
Impact of AC Distortion & Noise on Audio Equipment
and it exists and we can measure it, if we know what to do and we do not need a fancy equipment to make measurements. I know from thousands of measurements made on amplifiers that mains line load and frequency base load management (remote control from PWR distributor) do affect amplifier output, depending on its PSR.

An example of pretty usual consumer class AB amplifier measured at 25W/4ohm:

View attachment 145450
No extra mains load or control


View attachment 145451

View attachment 145452
The frequencies in red ellipses can also be detected as increased transformer mechanical noise.

I do not agree with conclusions in post #1.

I don't agree with your analysis either. So there.

All of your graphs are showing THD+N of 82.4. Even the decimal place doesn't change. That's because the performance of your device is characterized by strong harmonic distortions, not the mains/low frequency tones. Those tones are also not remotely audible at -100 dB. Your hearing threshold is whopping 50 to 60 dB higher than what you are showing there.

I don't even know what your analysis shows. Is that with three different AC feeds of differing quality? If so, show that as the start.

 

[solderdude]

Oh, I forgot to mention one real and quite obvious effect of clean AC sine. AC line distortions are mostly a 3rd harmonic which looks like a cutting of sine peaks. Power amps PS takes the current from that peaks, and in case of THD = 10% your power amp rails could be about 10% lower vs clean sine powered. It may sounds like more punch, more controlled bass, more solid and so on.

Well.. I don't know. Your example will simply show mains voltage will not be the expected 220V but measure at 206V.
The effect is that the time the rectifier conducts will be slightly different because it is flatter at the top.
The rectifier will still top up the reservoir caps but to a slightly lower DC value.

Let's take a power amp rated for 220W/4ohm with R to R output would need a +/- 42V rail voltage so the transformer would need to produce 30.8V AC with 220V AC in (it will never be a true sine anyway and will always be flattened.
On 206V AC the same transformer will provide 28.9V AC so 38.7V DC = 27.4V AC output = 187W/4ohm = 0.7dB less maximum output power.

I seriously doubt that one can hear a 0.7dB max output power (clipping level) will result in more controlled/solid bass given the fact that almost no one will be using their systems at clipping level.

 

[H-713]

Not really. Your power supply has reservoir capacitors. And is running at much lower voltages than mains. It also has feedback. So all this time everyone who doesn't have such devices has been losing bass, etc.? I don't think so.

What is going on with you all and these arguments?

I see where his argument is coming from, since most power amplifiers have unregulated power supplies (the voltage for which is directly determined by the step-down ratio of the transformer), but I'm also very unconvinced that a 10% reduction in the output power of an amplifier would be noticeable.

 

[IVX]

amirm, On the single punch, or on the first one 30VDC vs 33VDC rails(112W vs 136W of the peak power), it could be noticeable whatever the feedback loop gain is applied. At least you can easily measure the difference.

 

[amirm]

There is a clear logical fallacy of false syllogism occurring here.

Not really. Seems like you are watching a different channel than the one that the OP is on.

The tests so far have been:

There is a claim that poor audio equipment can benefit,
Here is a poor bit of equipment,
It didn't benefit,
Therefore, there do not exist any examples of equipment that can benefit.

This is junk, and the sort of crap arguments I would expect from the audiophool community.

The only junk is that analysis. The testing showed that incredibly distorted waveform did not move the measured performance of three different produce even the tiniest bit. Any propensity to sensitive of mains distortion should have moved the dial but it did not. It is as open and shut case as one can get.

Suddenly from this being a scientific exercise in measurement it has become one where the burden of proof is now on others to disprove the above fallacy of logic. In a science based forum this is depressing. Science has some serious problems in recent times, the reproducibility crisis being uppermost. Lets try not to go down the same path, and hold ourselves to a higher standard.

The only depressing thing is complaining about the test with pontifications. Or changing the topic to something it is not like audible hum, etc. You want to show your case, just post measurements like I have. Show how the analog output of the an audio product is impacted by fidelity of AC mains. Don't just create FUD around the work already done, must less do so in disgust.

 

[amirm]

I see where his argument is coming from, since most power amplifiers have unregulated power supplies (the voltage for which is directly determined by the step-down ratio of the transformer), but I'm also very unconvinced that a 10% reduction in the output power of an amplifier would be noticeable.

It is hand waiving nonsense. AC power is never at a set voltage. Are we to believe that the performance of our amplifier is constantly changing as AC voltage is??? Who would release an amplifier with such large and audible variations?

Yes, your peak power availability may be reduced due to voltage sag. What else is new? That has nothing to do with quality of the power.

 

[amirm]

amirm, On the single punch, or on the first one 30VDC vs 33VDC rails(112W vs 136W of the peak power), it could be noticeable whatever the feedback loop gain is applied.

What is noticeable? Distortion? No way. As I just explained, if you want to say your max power may be reduced due to lower voltage, sure. How are you going to make up for that lost peak voltage? No AC cleaner is going to give you higher voltage. Indeed, due to extra losses, you are going to get lower voltage. An AC generator can produce that but it is causing massive losses itself, resulting in less total power available to you.

 

[solderdude]

amirm, On the single punch, or on the first one 30VDC vs 33VDC rails(112W vs 136W of the peak power), it could be noticeable whatever the feedback loop gain is applied.

When there is a 33V DC rail on 220V the DC rail will be 30.8V on 206V.
22.6VAC out on 220V and 21.1V on 206V.
in 4 ohm = 127.7W vs 111W = - 1.2dB less maximum output power at the edge of clipping.

An (auto)transformer or an online UPS are the only devices that can return the sagging AC voltage line to its original voltage.

 

[IVX]

amirm, I hesitate to ask but do you know the difference between RMS and peak voltage?
The RMS voltage of a "dirty sine" will be even higher than the pure one, and at the same time Vpeak of the clear sine is higher.

 

[H-713]

Not really. Seems like you are watching a different channel than the one that the OP is on.


The only junk is that analysis. The testing showed that incredibly distorted waveform did not move the measured performance of three different produce even the tiniest bit. Any propensity to sensitive of mains distortion should have moved the dial but it did not. It is as open and shut case as one can get.

You tested three different products, all of which are relatively modern. All this shows is that those three particular products are not impacted. It does NOT show that all products are not impacted.

If I drive three modern cars without snow tires in a really bad snowstorm, and conclude that they do well in the snow, is it fair for me to conclude that snow tires are a scam?

 

[amirm]

@amirm, I hesitate to ask but do you know the difference between RMS and peak voltage?

My question back to you is do you understand asking irrelevant and pedantic questions?

The RMS voltage of a "dirty sine" will be even higher than the pure one, and at the same time Vpeak of the clear sine is higher.

So? It is not like you can filter the distortion and your peak voltage goes up. You are sucking up power in your filtering and you think that results in more energy available to your amplifier? Which school of engineering thought you that?

 

[pma]

This is one of the few products that would be worth testing.

https://www.accuphase.com/model/ps-520.html

 

[amirm]

You tested three different products, all of which are relatively modern. All this shows is that those three particular products are not impacted. It does NOT show that all products are not impacted.

Why you say that? You think people buy these boxes to only improve the performance of vintage products?

On what basis do you say other devices will act different?

 

[JohnYang1997]

You tested three different products, all of which are relatively modern. All this shows is that those three particular products are not impacted. It does NOT show that all products are not impacted.

If I drive three modern cars without snow tires in a really bad snowstorm, and conclude that they do well in the snow, is it fair for me to conclude that snow tires are a scam?

It is if the snow tires cost a few more times than the car.