Sources of Noise

[sandyk]

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.

[sandyk]

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.

[sandyk]

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.

 

[sandyk]

3 hours ago, Ralf11 said:

really any wall warts

 

Transformer based AC or DC wallwarts should not be of any real concern.

[sandyk]

You can  also still obtain AC wallwarts of up to 24VAC at 2A locally from places such as Wagner Electronics., as well as the lower current DC voltage types . (typically to 350mA.)

Gary

 

Another source of noise can be transformers buzzing annoyingly loudly due to due to DC offset of the A.C. mains supply.

 

https://sound-au.com/articles/xfmr-dc.htm

[sandyk]

Some poorly designed types of Asian LED lighting are well known for causing RF/EMI

 The attached is a link from an official Australian Government source.

 

https://www.acma.gov.au/Citizen/TV-Radio/Television/TV-reception/led-lights-and-tv-interference

[sandyk]

29 minutes ago, Ralf11 said:

https://audiophilestyle.com/forums/topic/56464-ac-line-noise/?tab=comments#comment-961748

 

That report was written 36 years ago, well before the proliferation of cheap and nasty SMPS and LED lighting etc.

 Much of the interference from them is radiated, not just carried via the A.C. mains supply.

 It even has the potential to disrupt Short Wave reception in many areas, as well as disrupt non local AM radio reception..

 This radiated rubbish may also affect some Audio equipment, especially when from items such as Refrigerators etc. cutting in and out.

[sandyk]

3 hours ago, Foggie said:

 

Are there better LED's then others?  Some LED strips use smps as well.  How does one use certain lighting (indirect lighting, spot lights, basically accent (cove) or mood lighting) in listening room without creating bad radiation? 

 

 

It's not the actual LEDs , it's the cheap and nasty SMPS that powers some cheap LED lighting.

Hopefully, this situation has improved recently.

[sandyk]

9 hours ago, Ralf11 said:

I just locate the computer & router far from the DAC.

 

On the other thread, I asked Sandy for some info to get a rough calculation of any radiation effects...

 I shouldn't need to tell you that spark transmitters were used in the very early days of Radio with transmissions often received several thousand miles away, so it should be obvious that even the momentary arcing of a thermostat etc. may result in interference at some considerable distance from the source. Whether or not it affects an electronic component will depend mainly on how resistant the designer has made it to external RF/EMI

[sandyk]

35 minutes ago, Ralf11 said:

It seems unlikely as the EMC from a router or computer is orders of magnitude less than a spark transmitter, which of course were designed to transmit.

 

Noise conducted along a USB cable seems a likely candidate for the worst offender, followed by power cables (either AC or DC).

 

I'd put radiated noise third and last.

 

Quote

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

 

You asked for sources of noise, and I have simply pointed out that AC mains aren't the only source of external electrical  noise and is more than capable of getting into a typical USB cable , not just from the source device itself

 In fact, you are well aware that many E.E.s even refuse to accept that what you have quoted as a likely candidate for the worst offender even matters at all.