Impact of AC Distortion & Noise on Audio Equipment

[Labjr]

Not sure what is causing noise in my system. The Marconi Spark Gap Transmitter or WLW's 500,000 watt AM transmitter in my backyard!

 

[solderdude]

yes, but that noise would consist of a constant high pitched sound that changes somewhat when the light is dimmed.
It would show up in an FFT as well as it is repetitive.
It will never be a tick unless when the lamp is switched on.
Due to the obligatory LC filter and filtering to ground in most SMPS those peaks may become asymmetric and common mode which some systems make audible.

 

[b4nt]

@solderdude Do you start to see the gap?

 

[tmtomh]

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.

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.

Once again, you are mischaracterizing the argument you're taking issue with. There's nothing unscientific about inductive hypotheses, so long as they remain hypotheses and not assertions.

The hypothesis is that the vast majority of audio equipment cannot in fact benefit from these AC cleaners, because - as @amirm has said in multiple places with admirable clarity - equipment already has to have plenty of internal AC filtering in order to simply perform at an acceptable level given how dirty most municipal power and household circuits can be.

Your complaint is simply that for such a hypothesis to be considered provisionally valid, we have to test N number of pieces of equipment, and Amir hasn't yet tested a large enough N. (And if you are tempted to say, "No, it's not the number it's the type of equipment, kindly don't - part of the problem with your logic here is that you're ruling out equipment as not proper examples after and based on the fact that the cleaners had no effect when Amir tested those examples.)

As noted in my prior response to you, I will be the first to agree that the current N=3 is not enough - and I'm sure many others here will too.

However, what you are not acknowledging is that Amir's tests of the two tube DACs have already altered and severely narrowed the definition of what counts as "poor" equipment for the purposes of trying to find a case where an AC cleaner makes a measurable difference. There is no reason to believe that these tube DACs have exceptional, special, or top-of-class AC filtering. All indications are that their internal filtering is garden-variety. And the AC cleaners make zero difference with them. Their high distortion is irrelevant, because as I noted in my last comment, there's plenty of AC-induced junk in the signal below the 1kHz test signal, which would be visibly changed on the graph had the AC cleaners done anything.

Put more simply, the burden is not on Amir or anyone else to prove that AC cleaners don't work by testing potentially 100s of pieces of gear to rule out a black swan that benefits. The burden is on the vendors of these cleaners to show something other than measurements of how the cleaners filter AC coming in from the wall socket. Unless or until they supply graphs of the output of audio equipment connected to them, which show significant measured differences in the audio equipment's output with vs without the cleaner in the chain, the rational presumption is that the cleaners don't work. You can't try to force Amir to prove a negative and then chide him and others for a logical fallacy.

Sorry to all those reading this to repeat myself, but once again what you're arguing for here is "poor in the precise right kind of way" equipment. That type of equipment might very well exist - and there might be many examples of it across different product categories from various manufacturers. But so far we've seen no evidence of it.

This isn't the 3x+1 problem in math (https://en.wikipedia.org/wiki/Collatz_conjecture), where the N number of examples you have to check in order to be reasonably confident of the truth (albeit still not achieving 100% mathematical proof) is in the quadrillions. The electrical and electronic characteristics and performance of typical AC filtering in audio equipment is well known - Amir doesn't keep writing that gear already has sufficient internal filtering because he's wildly speculating or guessing. There's sufficient evidence for a strong presumption in favor of Amir's statement in this regard - and the three DACs he tested is in addition to that. It's not like we were starting from 50-50 "who knows" territory before he tested them.

 

[solderdude]

Not sure what is causing noise in my system. The Marconi Spark Gap Transmitter or WLW's 500,000 watt AM transmitter in my backyard!

In my younger years I had a girl living next door. She used to play music really loud (radio). I quickly found a way to ensure the radio was turned down.
Had an electric razor. A Braun which was an inductor only (not a motor). When I almost plugged in the mains plug and jittered it around in the wall sockets sparks started flying around and radio reception turned into loud noise... worked like a charm.
That's EMC in action !

 

[Headchef]

So other than concluding that the topping a90 uses a PSU that can handle noisy power there’s not a lot more to this is there? Clearly it’s a quality headphone amplifier but this article doesn’t so much look into the effect of AC noise on Audio equipment, why not a power amplifier?

Did I miss it, was the a90 on low, medium or high gain? I’m assuming that high gain would have been used as it would have amplified any effects clearer?

johnyang1997 you might have missed my earlier reply to you?

 

[solderdude]

@solderdude Do you start to see the gap?

You are looking at 2 VERY different things.
The B&K signal creates the voltage a lamp loaded by a dimmer would see so behind the dimmer.
In this case the dimmer is 'set' so that after 35 degrees the triac starts conducting.

The small dips in the mains voltage (scope picture) show what the mains voltage before the dimmer.
In this case it would appear the dimmer is set in such a way that the triac starts conducting after 90 degrees.
You only see a short 'load and maybe LC filter' induced 'dip'.

 

[b4nt]

That's EMC in action !

I sniffed RF433 for my own needs. Catched something from the outside world. Didn't replay or test further, not knowing what that would have done outside

 

[Labjr]

I read that the WLW transmitter had it's own power substation.

 

[b4nt]

In this case it would appear the dimmer is set in such a way that

Either Amir tested how DACs behave in presence on common - and up to loud - noise on mains...

Or he could have tested feeding up to square to the DACs PSU and tested how they behave. Feed square to any DAC PSU, I think all will be nicely filtered out by PSU.

 

[David_M]

So other than concluding that the topping a90 uses a PSU that can handle noisy power there’s not a lot more to this is there? Clearly it’s a quality headphone amplifier but this article doesn’t so much look into the effect of AC noise on Audio equipment, why not a power amplifier?

The B&K noise simulator is only able to source 300VA of power. For a 120V system, that's only 2.5Amps in a perfect world. Power amplifiers require much more than 300VA to function, hence Amir's test on line-level equipment like the Topping HPA and the tube HPAs. The 300VA B&K noise simulator already costs about $5,500. I shudder to see what a full-blown 3000VA would cost, able to source 25Amps @ 120volts.

 

[GrumpyOldMan]

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

I have had a car like that.

 

[Wes]

might as well test a couple more DACs to hammer the nail in the coffin more firmly

 

[b4nt]

@solderdude Ask Amir to change the tittle, which currently is:

Impact of AC Distortion & Noise on Audio Equipment

 

[solderdude]

why ?
Amir measured the SINAD of an amp and of the (attenuated) mains voltage.

 

[Pdxwayne]

Testing with just 1khz with single device seems inadequate to me.

For example, Amir should be able to easily replicate what Furman does with a chain of devices, using null comparisons to show any differences, right?

Here is the screenshot of the Furman video that they used to demonstrate the difference. It is blurry, but the whole chain is listed. No amp involved....

 

[b4nt]

why ?
Amir measured the SINAD of an amp and of the (attenuated) mains voltage.

He tested SINAD of DACs, only adding distortion to sine AC, not noises.

 

[pma]

He tested SINAD of DACs, only adding distortion to sine AC, not noises.

Transient irregular waves are the issue - products of switching, RC ripple control of load. Harmonic distortion of 50 (60) Hz is unimportant, because every rectifier inside the amp makes more distortion to mains frequency wave.

 

[solderdude]

What would you call the mains from Amir which was also used ? On the right I see a lot of harmonics and lots of non harmonic 'poles' which I would describe as noise. Granted 70dB below the 110V so only 50mV or so.

 

[b4nt]

What would you call the mains from Amir which was also used ? On the right I see a lot of harmonics and lots of non harmonic 'poles' which I would describe as noise. Granted 70dB below the 110V so only 50mV or so.
View attachment 145623

I'd like to see some huge beats in between 5k and 100k, and listen how sensitive amps input stages, buffers and preamps would render those.