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Ralf11

Sources of Noise

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@jabbr mentioned a couple of days ago that a thread like this should be useful, so I am starting one - please stay on topic and indulge in worthwhile argument, not worthless ones or personal attacks

 

Let's leave signal cables aside for a while and start with the AC line (aka, mains).

 

Noise on the AC line can come from inside your house (or apt.) or from outside it.

 

This graph shows why noise sources down the block are unlikely to present an issue:

 

 

 

 

aa.jpg


"The overwhelming majority [of audiophiles] have very little knowledge, if any, about the most basic principles and operating characteristics of audio equipment. They often base their purchasing decisions on hearsay, and the preaching of media sages. Unfortunately, because of commercial considerations, much information is rooted in increasing revenue, not in assisting the audiophile. It seems as if the only requirements for becoming an "authority" in the world of audio is a keyboard."

-- Bruce Rozenblit of Transcendent Sound

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AC line noise often comes from:

a] Other hi-fi components, like big power amps with linear power supplies.

b] Other hi-fi components with SMPS power supplies.

c] any nearby wall-worts.

d] nearby appliances.

e] nearby hi-tech lighting systems.

f] HVAC

g] other entertainment, computer or network units.

 

 

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32 minutes ago, Ralf11 said:

Noise on the AC line can come from inside your house (or apt.) or from outside it.

 

Consider both differential & common mode noise & methods to reduce. The goal of AC PSU is typically to eliminate everything except 0 Hz ;) and lower output impedance at all reasonable frequencies ;);) 


Custom room treatments for headphone users.

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22 minutes ago, Speedskater said:

AC line noise often comes from:

a] Other hi-fi components, like big power amps with linear power supplies.

b] Other hi-fi components with SMPS power supplies.

c] any nearby wall-worts.

d] nearby appliances.

e] nearby hi-tech lighting systems.

f] HVAC

g] other entertainment, computer or network units.

 

 

Back in the old days, florescent lights with the associated ballast was often a big source of noise (pretty much covered by 'nearby appliances' in the list above.)   I dont' know of those pollution prone mini-florescents are bad at all though.

 

John

 

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1 hour ago, jabbr said:

 

Consider both differential & common mode noise & methods to reduce. The goal of AC PSU is typically to eliminate everything except 0 Hz ;) and lower output impedance at all reasonable frequencies ;);) 

Or it can be an additional source of noise, interference and current limiting problems.

"Consider both differential & common mode noise" this is over thinking the problem.

It's not something the experts like:

Ralph Morrison

Henry Ott

Keith Armstrong

Jim Brown

Bill whitlock

spend much time on.

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1 hour ago, John Dyson said:

Back in the old days, florescent lights with the associated ballast was often a big source of noise (pretty much covered by 'nearby appliances' in the list above.)   I dont' know of those pollution prone mini-florescents are bad at all though.

John

Burnt-out CFL's can be a source of intermittent noise. You think that they are turned off, but they are sitting there arcing and sparking.

Another intermittent noise source is a bad doorbell transformer. Most people don't even know that they have one.

 

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Even a large industrial building >100M away may cause noise despite a transformer on a pole not far away.

 In apartment blocks, lifts can also cause problems.

 A poor mains earth (e.g. corroded) at the premises can also result in a lot of electrical noise from external sources.


"If you can't hear the difference between an original CD and a copy of your CD,

you might as well give up your career as a tester. The difference between a reconstituted FLAC and full size WAV is much less than that, but it does exist. - Cookie Marenco"

 

PROFILE UPDATED 18-06-2019

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refer to the graph in post #1 as a guide (30 m)  - you are talking 3x that, plus a transformer (a pole mount I guess), so how much noise would you expect?  1/3 dB down at 100 m for 10 kHz, not counting the transformer, while not much distance helps

 

I agree with your other points, but zoning law help with noise on the AC line (tho a ham radio operator next door could be a problem)


"The overwhelming majority [of audiophiles] have very little knowledge, if any, about the most basic principles and operating characteristics of audio equipment. They often base their purchasing decisions on hearsay, and the preaching of media sages. Unfortunately, because of commercial considerations, much information is rooted in increasing revenue, not in assisting the audiophile. It seems as if the only requirements for becoming an "authority" in the world of audio is a keyboard."

-- Bruce Rozenblit of Transcendent Sound

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41 minutes ago, Ralf11 said:

refer to the graph in post #1 as a guide (30 m) 

I don't give a damn for your guide . I am reporting what I have found in practice, as well as in Telephone Exchange maintenance as a Principal Telecommunications Technical Officer, where  a nearby railway station can result in occasional problems, and a large shopping centre several hundred metres away down the road can cause problems when initially starting up the complex in the morning, even occasionally blowing out a large Exchange rectifier.

Earthing is the main culprit in  situations like this.

27MHZ  CB radio operators are far more likely in my experience to cause problems as the  ham radio operators are required to meet quite stringent transmission standards.


"If you can't hear the difference between an original CD and a copy of your CD,

you might as well give up your career as a tester. The difference between a reconstituted FLAC and full size WAV is much less than that, but it does exist. - Cookie Marenco"

 

PROFILE UPDATED 18-06-2019

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That isn't "my" guide, nor is it it a "guide."

 

But thanks for your anecdote about telephone exchanges.  Let's keep this thread on audio.


"The overwhelming majority [of audiophiles] have very little knowledge, if any, about the most basic principles and operating characteristics of audio equipment. They often base their purchasing decisions on hearsay, and the preaching of media sages. Unfortunately, because of commercial considerations, much information is rooted in increasing revenue, not in assisting the audiophile. It seems as if the only requirements for becoming an "authority" in the world of audio is a keyboard."

-- Bruce Rozenblit of Transcendent Sound

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11 minutes ago, Ralf11 said:

That isn't "my" guide, nor is it it a "guide."

 

But thanks for your anecdote about telephone exchanges.  Let's keep this thread on audio.

 

 Earthing practices has EVERYTHING to do with Audio !!

This particularly applies to apartment blocks etc.

 


"If you can't hear the difference between an original CD and a copy of your CD,

you might as well give up your career as a tester. The difference between a reconstituted FLAC and full size WAV is much less than that, but it does exist. - Cookie Marenco"

 

PROFILE UPDATED 18-06-2019

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2 hours ago, Speedskater said:

AC line noise often comes from:

a] Other hi-fi components, like big power amps with linear power supplies.

b] Other hi-fi components with SMPS power supplies.

c] any nearby wall-worts.

d] nearby appliances.

e] nearby hi-tech lighting systems.

f] HVAC

g] other entertainment, computer or network units.

h] Alex

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28 minutes ago, sandyk said:

 Earthing practices has EVERYTHING to do with Audio !!

This particularly applies to apartment blocks etc.

Now that's confusing. What do you mean by earth/ground? The words have so many different meaning and so many incorrect meaning.

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6 minutes ago, Speedskater said:

Now that's confusing. What do you mean by earth/ground? The words have so many different meaning and so many incorrect meaning.

Yea -- all of those terms are used interchangably and can be confusing when actually doing the circuit layout if taken literally.  The goal is to make sure that there are no digital currents intermixed through an analog common return path.   So, don't hook the 'ground' or '0V' pin of a digital chip onto the analog common return path.  There is an adage -- keep the digital and analog grounds separate, and that is a good 1st order guideline, but doesn't solve the interference problem entirely.   'Ground noise' as it is sometimes called, is usually a prominent noise source, but not the only one.   When dealing with chips with 100amp sub-ns wide spikes -- that is a huge opportunity for developing a voltage across a very short wire.   Thems digital chips are the culprits (even though usually only CPUs are the evil 100amp sources, but still -- even more normal digital parts can be pretty noisy.)

 

PS -- also need to be careful about where bypass capacitors go.

 

John

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Don't forget PLC (power line communication) a source of noise, but also a source for information on mains based noise, as the PLC has to cope with the noise on the lines to get the signals through.

https://pdfs.semanticscholar.org/d919/6f31ff00559642af4e5930d9fe7f2c0c4bf4.pdf

 

Mains noise can vary from country to country and area to area, dependant on local industry, power generation methods, regulation (law) and how closely its controlled etc.

Interesting on how changing from traditional power generation is having an effect on the power grids inertia.

http://watt-logic.com/2017/10/12/inertia/

 

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I live right next to a massive casino & multiple hotel complex and initially thought I'd have possible issues with power but have been surprised by how stable my AC supply is when I've measured it and how little affect power conditioners have had in my setup, keeping in mind that I live in a city that is renowned for it's inconsistent power supply compared to the rest of the country. I have been told that the casino complex has spent a fortune on some sort of power conditioning.

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It is very well known that the mains doesn’t look like in the textbooks anymore. It’s because of the common use of non-linear electrical loads from gear both in our home, office and industry. If you actually would measure THD and DC offset on the mains you would see that they aren’t perfect sinewaves and that they oscillate a lot. The constant fluctuation on the AC line is kind of devastating for sensitive gear and circuits. One of the most sensitive device is clocks (oscillators), which is why they are used to measure noise with. Other circuits that doesn’t operate well with AC/DC noise and voltage fluctuation are regulators, tubes and the dac chip. All commonly used and of great importance in many audio gear.

 

 

 

http://www02.abb.com/global/seitp/seitp202.nsf/0/f719148022b816dcc125770300214644/$file/ABB+Harmonics+%26+Solutions.pdf

https://www.picotech.com/library/oscilloscopes/mains-harmonic-measurements

https://www.allaboutcircuits.com/technical-articles/the-importance-of-total-harmonic-distortion/

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1 hour ago, asdf1000 said:

 

Can you upload this PDF. It's currently linked to your C drive

 

I think that it is a Power Point:

"Fundamentals of EMC, Grounding"

by John McCloskey

NASA/GSFC Chief EMC Engineer

 

From the above link and other links.

 

He does spent time on 'common mode' problems.

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