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Where does EMI/EMC, leakage current, common mode noise and other considerations belong on the "audibly the same" discussion?

HaveMeterWillTravel

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Where does EMI/EMC, leakage current, common mode noise and other considerations belong on the "audibly the same" discussion?

I get the general sense that many (most?) here do not consider EMI/EMC effects and other more nuanced design performance may never fall within the discussion of audibility, and should be cast out to seemingly oblivion. I am of the opinion that it does a disservice. Take for the example two otherwise equal USB DACs but where one may require the use of a USB isolator to prevent audible "hum" and the other does not. To an individual it clearly has an audible difference in his system! How does telling that indiviudal there is no audible difference a furtherance to a scientic method?

The standard caveat to disregard the effects by adding "properly engineered" has been rendered to the status of a near tautology. In large part because it is applied post hoc. A "yes yes, but .." type response. Yet one could that any device with single-ended chassis/ground referenced signal interconnects are not "properly engineered" since there are superior designs out there.

Unlike frequency response, gain setting, SINAD and other areas of known audible difference, the audio sphere rarely discusses where and when audible effects occur. Nor is it measured prior to proclaiming there are no audible differences between two devices.

It's niave to think audio equipment will be designed and tested to a level as to have no possibility of audible effects, yet it's not pactical to test them. Even if a product is susceptable, whether or not it ever manifests itself is higly specific to the individual circumstances. Some of us older folk may remember when certain TV's would have 'noise' when certain hairdryers were used. If you had the TV yet no one used those hairdryers in your household, you never saw it.

Does it have a legitiment scientific place in discussions of (possible) audible differences?
Or does it contaminate the "Gospel"?

This is a quandry.

HMWT
 
Part of this comes down to the informal and collective expectations for types of audio gear and behavior. Take for example a magnetic moving cartridge. Due to its very nature, it and the required circuitry may be very susceptible to magnetic fields. Placing it directly on top of a high-current transformer may lead to all kinds of issues. Yet do we use that in-itself to say it is not engineered properly?

How about some recently posted examples: audible noises, pops, clicks, etc. from dimmable LED lights, a dryer turning on or off? Are all the components “not properly engineered” even if it may only affect a tiny fraction of their customers?

Now, consider the various cases of “hum”, or “ground loop”. Or, where USB or other digital connections may have sporadic communication issues or outright stop communicating. There’s plenty of discussions on analog or digital isolation. What is the collective expectation on “engineered properly” for these examples?

What about a device where it is perfectly fine by itself, but when interconnected with another device it may have issues. What if the root cause is not with the device, but really stems from a deficiency with the other device?
 
Trying to redirect some discussions to here. I am unsure if they'll get a notice.

https://audiosciencereview.com/foru...d-cannot-make-a-difference.56623/post-2201198

" After 100s of kilometers of high voltage transmission lines, transfer stations, regional transmission lines, substations, local transmission lines, neighborhood transformer, neighborhood lines, domestic power meter, domestic circuit breaker box, home wiring, and finally your outlet. And somebody actually thinks the final 1m of wire will make a difference? I understand the psychology. It's because it's the only 1m of wire the normal person pays attention, although there's a circuit breaker box somewhere in the house, a power meter on the side of the house, a neighborhood transformer at the end of the row, utility lines out at the street, a substation surrounded by a fence on the property behind the community library, and big transmission towers leading out of the city ... "

For many devices, the final 1 to 2" may be the most important. That is, the EMI/RFI filter typically integrated into the IEC A/C power receptacle.
I personally like not having audible pops or clicks when the HVAC kicks in, or the dryer turns on.


 
Measurements?
 
Take for the example two otherwise equal USB DACs but where one may require the use of a USB isolator to prevent audible "hum" and the other does not.

Obviously here if the problem is solved with a USB isolator, then we are (by far most likely) talking about a ground loop.

Thing is a ground loop is a system issue, not an issue for an individual component. It requires two ground connections on either end of an analogue interconnect (or another loop formed for example by multiple direction analogue interconnect. And it requires a source of ground current.

Take a typical setup of PC>DAC>AMP. In a ground loop situation, most commonly the PC and AMP have ground connections, and more often than not the PC is the source of ground noise. The DAC is just the middleman in this situation, simply passing the ground currents from input to output. The fact it can be solved with USB isolation, or use of TOSLINK as the connection to the DAC does not make it a problem caused by the DAC. In fact a Class I dac with a ground connection might actually elminate the problem as (some of the) ground current can go to ground directly from the DAC rather than having to go through the analogue interconnect and on to the amp.

This is perhaps tricky to explain to a layperson, and it is understandable that they might get confused, and think it is the fault of one particular component.
 
Nor is it measured prior to proclaiming there are no audible differences between two devices.
The reason for that should be obvious. Noise - whether it is ground loop borne, or conducted or radiated EMI, is always a system problem. It requires a noise source, a coupling mechanism and a device to be impacted.

That will always be complex, dependent on the exact arrangement of components and interconnect, and dependent also on the electrical environment in which it is installed. It is not possible for a component to be tested in a way which will be relevant to the end user - because every end user situation will be different. The only tests which can reasonably be carried out are the type approval tests done by the manufacturer according to the appropriate standard - eg the IEC61000 set of standards. These are obviously way beyond the scope of any reviewing organisation.

I could bring two devices home and try them both. One might result in audible noise, where the other is dead silent. I could give those two devices to you and the noisy/quiet one might be reversed in your system.

I think it is also fair to say that the vast majority of setups don't experience any audible noise at the listening position. Or if they do it is not really objectionable. The best we can do here is try to help people solve their issues when they arise.


Some of us older folk may remember when certain TV's would have 'noise' when certain hairdryers were used.
You don't have to be old. My sub hums when Mrs AC switches her hair straigners on. I think they use half wave rectification on the low power setting she uses, and stick DC on the line. Or possibly they have some sort of thyristor controlled rectification that messes things up.

It doesn't bother me much since it is only for about 10 minutes each morning. :)
 
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That is, the EMI/RFI filter typically integrated into the IEC A/C power receptacle.
I don't have any gear with a filter integrated into the IEC receptacle. I'm not sure Ive ever seen any home AV kit that has.
 
Thing is a ground loop is a system issue, not an issue for an individual component. It requires two ground connections on either end of an analogue interconnect (or another loop formed for example by multiple direction analogue interconnect. And it requires a source of ground current.
A Zen koan for the electric age: "What is the sound of one ground looping?"
 
Lifting ground unsafe.
What do to? Look at Toslink.
So perfect, so clean.
 
To an individual it clearly has an audible difference in his system!
The thing is that such audible gremlins are audible as hum, noise, ticks or whatever, especially in quiet passages.
The 'audible differences' people report are more remarks like: blacker background, more air, and other 'sound quality improving things that could just as easily be applied to cables, mains fuses, and whatnot.

Those people never talk about weird hums, noise, etc. where those would be the audible differences one would encounter. So ... I say no to 'sound improvements' but yes to people complaining about unwanted and not music related sounds that clearly don't belong.

Now, consider the various cases of “hum”, or “ground loop”. Or, where USB or other digital connections may have sporadic communication issues or outright stop communicating. There’s plenty of discussions on analog or digital isolation. What is the collective expectation on “engineered properly” for these examples?
When digital connections are disturbed one gets ticks, noises (usually loud) and drop-outs. Not a 'degradation' of stereo imaging or less deep bass etc.

Digital to analog isolation is not always needed. It highly depends on the situation and actual DAC construction as well as the analog output construction.
Amir does NOT test for this nor is this the scope of ASR. That only looks at signal fidelity.
Whether or not any DAC or amp in any combination in some specific situation at home connecting multiple devices might or might not be functioning as expected or 'gremlins' that may or may not reach audible thresholds in the system is not possible to test. In fact no one tests for this nor can one simulate all possible conditions where such may occur.

Everyone that ever did EMC testing and found some weird frequency to influence the connected gear, changes a simple connector or a cable/wire routing and it then it passes the required test(limits) would certainly know how complex that is. Again, this is irrelevant for any audio testing, also because those limits in practice are never reached and even then one could simply state that during that test a specific amount of influence is allowed (within tolerances) so...

This is not a collective expectation of engineering but only lives in minds of engineers/designers that actually test for those things or have it tested.

Ground loops can be avoided and can be solved. Sometimes it isn't easy because not all relevant info on the actual circumstances in someone's home situation is known.
What about a device where it is perfectly fine by itself, but when interconnected with another device it may have issues. What if the root cause is not with the device, but really stems from a deficiency with the other device?

Yep, that would need to be handled in situ. All information should be available for remote trouble shooting. Device A can work problem free in a situation and be plagued by whatever gremlins in another situation. And it would be nigh on impossible to test for all or even a couple of situations as those might differ from the actual situation where it occurs.
For many devices, the final 1 to 2" may be the most important. That is, the EMI/RFI filter typically integrated into the IEC A/C power receptacle.
I personally like not having audible pops or clicks when the HVAC kicks in, or the dryer turns on.
Many devices ? a 'regular' mains cable ? filters are usually inside the gear NOT in the cable.
I seriously wonder how many people fixed problems with hum or other nasties by using an expensive cable.
When you hear ticks when switching on other things in the home something simply isn't correct. Good luck trouble shooting that without (expert) knowledge and iterative steps in testing.
And even when one hears a 'tick' in some systems when something happens on the mains it does not change the 'sound' nor 'sound quality' of the system. One just hears a 'tick'.
Vinyl lovers can relate.

This is not solved with a different mains cable in general either but requires a bit more attention.
 
Where does EMI/EMC, leakage current, common mode noise and other considerations belong on the "audibly the same" discussion?

I get the general sense that many (most?) here do not consider EMI/EMC effects and other more nuanced design performance may never fall within the discussion of audibility, and should be cast out to seemingly oblivion. I am of the opinion that it does a disservice. Take for the example two otherwise equal USB DACs but where one may require the use of a USB isolator to prevent audible "hum" and the other does not. To an individual it clearly has an audible difference in his system! How does telling that indiviudal there is no audible difference a furtherance to a scientic method?

The standard caveat to disregard the effects by adding "properly engineered" has been rendered to the status of a near tautology. In large part because it is applied post hoc. A "yes yes, but .." type response. Yet one could that any device with single-ended chassis/ground referenced signal interconnects are not "properly engineered" since there are superior designs out there.

Unlike frequency response, gain setting, SINAD and other areas of known audible difference, the audio sphere rarely discusses where and when audible effects occur. Nor is it measured prior to proclaiming there are no audible differences between two devices.

It's niave to think audio equipment will be designed and tested to a level as to have no possibility of audible effects, yet it's not pactical to test them. Even if a product is susceptable, whether or not it ever manifests itself is higly specific to the individual circumstances. Some of us older folk may remember when certain TV's would have 'noise' when certain hairdryers were used. If you had the TV yet no one used those hairdryers in your household, you never saw it.

Does it have a legitiment scientific place in discussions of (possible) audible differences?
Or does it contaminate the "Gospel"?

This is a quandry.

HMWT
EMI is customer location specific. Some equipment is required to conform with FCC Part 47 and Part 15 rules, but that does not cover most audio equipment.

Not sure what you mean by leakage current. If you are talking about mains or power supply coupling to the chassis, it will be conducted back to the mains ground. It is a safety issue, not audible.

Not sure what you mean by common mode noise. The main point of balanced inputs is the common mode rejection ratio on the input side.

All of them are things that are extremely difficult to test in a standard way, rare to find in today's equipment, and easy for the customer to rectify.
 
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Obviously here if the problem is solved with a USB isolator, then we are (by far most likely) talking about a ground loop.
..
.. It requires two ground connections on either end of an analogue interconnect (or another loop formed for example by multiple direction analogue interconnect. And it requires a source of ground current.


It may or may not actually be due to a 'ground loop', or rather, current flow through the ground which creates a voltage potential between the two devices signal references, which may or may not be related to ground. For example, it can still occur between devices which have no ground connection at all such as the traditional "two wire" across line and neutral. The clearest case would be aboard boats/ships where there is inherently no ground connection.

Rather, I would wager that it generally involves a effects of leakage currents of one or either device causing common mode noise..


Thing is a ground loop is a system issue, not an issue for an individual component.

I have to disagree as a devices susceptibility to a certain level of common mode noise can be and in these cases are most definitely a 'fault' of the individual component itself.
Whether or not it affects a particular interconnected system is a separate issue.

That is one of the principle concepts of EMC: electromagnetic compatibility. Emissions generally are concerned on if the introduction of the device CAUSE undesirable misbehavior in equipment which otherwise meet a certain level of immunity. Is it 'yelling' louder than what would be an otherwise defined ambient RF environment. Susceptibility/Immunity considers the case on if the device will properly function in a defined ambient RF environment

While common EMC test methods often do not test for common mode emissions, nor do I think they are generally regulated for consumer audio equipment; the maximum "touch current" is for safety reasons. Which frequency causes the main constitute of common mode emissions.

I would postulate that any piece of equipment which may suffer susceptibility issues with common mode noises which fall under this level *IS* an improperly engineered piece of equipment.
Take a typical setup of PC>DAC>AMP. In a ground loop situation, most commonly the PC and AMP have ground connections, and more often than not the PC is the source of ground noise. The DAC is just the middleman in this situation, simply passing the ground currents from input to output. The fact it can be solved with USB isolation, or use of TOSLINK as the connection to the DAC does not make it a problem caused by the DAC. In fact a Class I dac with a ground connection might actually elminate the problem as (some of the) ground current can go to ground directly from the DAC rather than having to go through the analogue interconnect and on to the amp.

First I would ask how the problem presents itself. Does it affect the digital communication between the PC and DAC. Or the analog signal between the DAC and the amp?
If the DAC is expected to be compatible with a PC, then it bloody well should be comparable with a PC under any and all (reasonable) use cases!

Shunting common noise related to line power to power ground is a method to reduce the magnitude of it. But while it is commonly used as 'ground noise', it is not. The noise is not being generated from the 'ground'.

This is perhaps tricky to explain to a layperson, and it is understandable that they might get confused, and think it is the fault of one particular component.

Please refrain from contaminating topics with the 'common noise' of ad hominem attacks and casting aspersions at others .
But, if you do with to make a an appeal to authority in the EMC area, are you iNARTE certified for EMC?
 
I have to disagree as a devices susceptibility to a certain level of common mode noise can be and in these cases are most definitely a 'fault' of the individual component itself.
Only in as much as an unbalanced analogue connection is always susceptible to common mode noise. in fact on the interconnect it isn't common mode at the receiving end at all - it is only on the signal, relative to local ground). Other than provide balanced interconnect, there is little the device can do about this.
 
The thing is that such audible gremlins are audible as hum, noise, ticks or whatever, especially in quiet passages.
The 'audible differences' people report are more remarks like: blacker background, more air, and other 'sound quality improving things that could just as easily be applied to cables, mains fuses, and whatnot.

You are presupposing statements of fact which are not contained in this thread.

Those people never talk about weird hums, noise, etc. where those would be the audible differences one would encounter.

Ah, the anamorphic but "those people". Are they here?

So ... I say no to 'sound improvements' but yes to people complaining about unwanted and not music related sounds that clearly don't belong.
"sound improvement" is a subjective description, even if Im' sure the vast majority of people will agree on it.
I would consider it as being one of the most obvious and mostly unquestioned audio differences possible.

When digital connections are disturbed one gets ticks, noises (usually loud) and drop-outs. Not a 'degradation' of stereo imaging or less deep bass etc.

You are presupposing statements of fact which are not contained in this thread.

Digital to analog isolation is not always needed.

I agree on 'isolation'. However, the fault may not be due to a 'lack of isolation'.

It highly depends on the situation and actual DAC construction as well as the analog output construction.
Amir does NOT test for this nor is this the scope of ASR. That only looks at signal fidelity.
Whether or not any DAC or amp in any combination in some specific situation at home connecting multiple devices might or might not be functioning as expected or 'gremlins' that may or may not reach audible thresholds in the system is not possible to test. In fact no one tests for this nor can one simulate all possible conditions where such may occur.
All possible conditions? Sure. But why shouldn't the common expectation be the equipment will function as designed in most reasonable applications?

Its 2025, any USB DAC which is not comptable with common computer hardware is just poorly designed. IMHO.



Everyone that ever did EMC testing and found some weird frequency to influence the connected gear, changes a simple connector or a cable/wire routing and it then it passes the required test(limits) would certainly know how complex that is. Again, this is irrelevant for any audio testing, also because those limits in practice are never reached and even then one could simply state that during that test a specific amount of influence is allowed (within tolerances) so...

This is not a collective expectation of engineering but only lives in minds of engineers/designers that actually test for those things or have it tested.

Weird, I would have hoped the collective expectation of audio equipment buyers would be that the equipment they purchase would be compatable with the other equipment when featuring the same type of interface. e.g. USB to USB, RCA to RCA, XLR to XLR, toslink to tosklink.


Ground loops can be avoided and can be solved. Sometimes it isn't easy because not all relevant info on the actual circumstances in someone's home situation is known.
How about products which do not have ground loop issues under normal installation and usage?

Yep, that would need to be handled in situ. All information should be available for remote trouble shooting. Device A can work problem free in a situation and be plagued by whatever gremlins in another situation. And it would be nigh on impossible to test for all or even a couple of situations as those might differ from the actual situation where it occurs.

Many devices ? a 'regular' mains cable ? filters are usually inside the gear NOT in the cable.
Might I point out that this is a new thread?

I seriously wonder how many people fixed problems with hum or other nasties by using an expensive cable.
I seriously wonder how many people have brought products to 'fix' preexisting problems in equipment which ought not to have it?

When you hear ticks when switching on other things in the home something simply isn't correct. Good luck trouble shooting that without (expert) knowledge and iterative steps in testing.
And even when one hears a 'tick' in some systems when something happens on the mains it does not change the 'sound' nor 'sound quality' of the system.
You keep repeating this strawman when it isn't germain to the topic.

One just hears a 'tick'.
Vinyl lovers can relate.

This is not solved with a different mains cable in general either but requires a bit more attention.
Might I point out that this is a new thread?
 
Here in Italy every hundred meters there is a pylon with countless mobile phone repeaters.
They are above the apartments and civilian houses because the telephone companies pay a lot of rent for these roofs to private citizens.
Yet, both because all the electrical systems in our homes are made to standards, and because all the equipment I purchase complies with regulations, there is not a single component of my system that is "disturbed" by EMI/EMC.
 
Only in as much as an unbalanced analogue connection is always susceptible to common mode noise.
There are several techniques to have unbalanced connections which are far less susceptible to common mode noise. The audio industry chooses not to use them. Not that I am arguing that they should, mind you.

in fact on the interconnect it isn't common mode at the receiving end at all - it is only on the signal, relative to local ground). Other than provide balanced interconnect, there is little the device can do about this.

And yet, common mode noise exists in systems which inherently do not have ground.

Hmm...
 
Here in Italy every hundred meters there is a pylon with countless mobile phone repeaters.
They are above the apartments and civilian houses because the telephone companies pay a lot of rent for these roofs to private citizens.
Yet, both because all the electrical systems in our homes are made to standards, and because all the equipment I purchase complies with regulations, there is not a single component of my system that is "disturbed" by EMI/EMC.
For the end consumer, isn't it great when one can buy a peice of equipment and have good assurance it will 'just work' as in, be comptable with the ambient RF enviroment?
 
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