EMI/RFI thoughts and discussion on its management via cables etc

[amirm]

Funny that this thread got refreshed the same time my son asked me for effects of EMI radiation on a DAC. So we set up a quick test.

I used two DACs: the iFi iDAC2 and $20 FiiO Taishan. I put my audio precision analyzer in continuous measurement mode and persistence (i.e. having graphs pile up on top of each other). I played my usual high frequency tone and watched the response. It was very consistent.

My son then ran a 3-D benchmark on his phone that maxed it out good. I proceeded to put the phone both on his back side and face (LCD) side on the DAC. There was zero leakage into either DAC!

The connection between the DACs and my AP were a cheap, free audio+video cable that came with my DVD player years back. It was as thin as you can imagine. I proceeded to put the phone on it. Again, absolutely no change in response even in the $20 DAC.

I then extended the measurement to 130 Khz to see if anything shows up there. Again, the results did not change whatsoever.

Reason is simple of course. While the phone is radiating like crazy, the components run well above the frequencies we care about/measuring. Very little happens at such low/audio frequencies and those events get shielded by the metal boxes of DACs and cable shielding.

I might do more analysis at a future date but right now, "this dog don't hunt."

 

[RayDunzl]

Somebody comes up with a neutrino shield though, I'm all ears.

 

[watchnerd]

Somebody comes up with a neutrino shield though, I'm all ears.

That's easy, just use degenerate matter.

 

[RayDunzl]

Noise in my Degenerate system and home:

I have no shields on the DAC to Pre nor Pre to Amps.

Cable management, at this time, is restricted to having the ends plugged in where they need to go. It's a rats nest back there after several years.

I can't pick out any difference in the measurements attributable to noise coming from the speakers.

 

[Sal1950]

The connection between the DACs and my AP were a cheap, free audio+video cable that came with my DVD player years back.

And they call me the Audio Cheapskate! LOL

 

[RayDunzl]

The connection between the DACs and my AP were a cheap, free audio+video cable that came with my DVD player years back.

And they call me the Audio Cheapskate! LOL

You plug it in, it works, and you forget about it. At least I do. Those skinny red/white/yellows separate nicely into single runs, too.

 

[RayDunzl]

EMI/RFI thoughts and discussion on its management via cables etc

EMF at the rack:

I just pulled out my 1963 (or so) RCA 8 Transistor 9V battery AM Nerd Pocket Radio and waved it around near the gear.

The plasma TV makes a ferocious amount of noise.

The Behringer DEQ2496 comes in second, only slightly less unbelievable.

Next comes the flourescent displays on the cable box and the CD player

The rest of the stuff isn't nearly as obvious, more of a general digital murmur, didn't pinpoint anything else.

None of it comes out of the speakers, as near as I can tell, measuring with my trusty microphone and my less trusty ears.

 

[Sal1950]

You plug it in, it works, and you forget about it. At least I do. Those skinny red/white/yellows separate nicely into single runs, too.

But OH THE VEILS INTRODUCED!
It's like putting Amber Heard in a Niqab.

 

[Blumlein 88]

EMF at the rack:

I just pulled out my 1963 (or so) RCA 8 Transistor 9V battery AM Nerd Pocket Radio and waved it around near the gear.

The plasma TV makes a ferocious amount of noise.

The Behringer DEQ2496 comes in second, only slightly less unbelievable.

Next comes the flourescent displays on the cable box and the CD player

The rest of the stuff isn't nearly as obvious, more of a general digital murmur, didn't pinpoint anything else.

None of it comes out of the speakers, as near as I can tell, measuring with my trusty microphone and my less trusty ears.

I did the same test using a hand-held radio which did SW, VHF, AM and FM. Did not use the FM. On the others there was a tremendous difference with no consistency between different PC hardware. I had 3 laptops and 2 desktops on hand all running the same Windows OS. The idea player software can be written to lower EMI-RF issues in audio is ridiculous for at least two reasons. One is what you have shown in that one can't find any sound difference due this other high frequency noise. The other is that software will emit wildly different RF on different hardware. One could specify hardware and software, but you still have to show an in room sound difference resulting from it. There was also tremendous differences in where RF was clustered if you changed the OS on a given piece of hardware. I did this with a couple different Linux distros and a BSD distro. All of them were different. All differed as the hardware differed too. Plus one of the big bonuses of digital signal tranfer/transmission is immunity to environmental noise. Trying to turn around and act as if digital has 'analog-like issues' or the oft touted idea digital isn't, even digital signals are just analog is such total garbage and weak minded thinking that combined with a total lack of evidence you might think such ideas would dissappear rather than grow, multiply and help sellers of solutions to non-problems prosper. Wishful thinking on my part.

 

[fas42]

You won't get "noise" out of the speaker with these sort of issues, but the 'quality', tonality changes. And if you 'tune' into the characteristic of these changes they become very easy to register. People won't hesitate to say that if the speakers are changed then the sound "will change" - well, for me, I hear that "change of speakers" when there is the presence, or absence, of EMI isssues; to get a handle on it, it's going from a very average tweeter, to one of the highest quality ones one could put in, when EMI is not there. So, how easy is it to show, with relevant measurements, what is now "better" on the speaker with the superior tweeter?

Digital circuitry is electrical circuitry, fed by power supplies which have lots of analogue like modulation of the voltages throughout the circuit board, depending on what digital processing is happening, how well the board was engineered, the quality, and age of the smoothing capacitors used - and signals modulating when theoretically they are fixed in level leaves open the possibility that there is interference coupling.

 

[bailes]

Very interesting Roger D, please would you expand on how chassis grounding of hifi audio components should be done in practice. Is it just as simple as connecting all the audio components together to a single point and then taking this single point to good earth point (on the mains supply in the UK)?

 

[pedrob]

My setup is dead silent as far as I can tell, and I've taken no "care" with pedigreed cabling. I even have some single conductor un-shielded and virtually un-insulated magnet wire interconnects still connected, as an experiment to "see what happens". In my case, I rate all your concerns as "not a problem here".

I live in a modern suburban neighborhood, with all that that entails, with the area's main transmitter farm about 3 miles away, several cell towers closer, CFL and Fluorescent lights, a PC in an open case, you name it as a potential problem, and I probably have it in the air.

I have cell phones and wifi and bluetooth and a "noisy" plasma TV - but the audio exhibits no audible nor measurable (with the tools I have) defect.

On the other hand, my Dad used to be a Ham Radio Operator, and when he fired up his high-power transmitter, then you could tell every time he fingered the transmit key. There would be nasty problems on the TV video and audio, etc., - but that was many years ago now.

Ray, point well taken although I believe it is more likely to contaminate the signal than the silence.

 

[RayDunzl]

Ray, point well taken although I believe it is more likely to contaminate the signal than the silence.

That's some smart interference.

 

[pedrob]

Don, I doubt Walter implies a cable makes noise. Though there is a concept of shield induced noise,but I really don't think that is implied either. I think RFI is a non issue in high end cables. Magnetic interference produced by current is the larger issue in audio equipment in general,but grounding schemes can help in that regard. There is a lot we do not understand yet...but I believe we are getting closer. Thanks

Roger, well said. I do wonder though if the progress could/should be sped up.

Interference is all around us in the atmosphere and it's impact on music is poorly understood. We can easily see its impact on a simple sine wave, but what about contamination of complex music? Noise is not selective and digital square waves are not immune: I am constantly amazed it is claimed that equipment can magically identify the digital noise and remove it. At best the noise is averaged before filtered out; at best an imperfect solution. Power supplies in players can easily contaminate the signal at the source.

Atmospheric contamination can also come from local sources such as power cables and this is why shielded cables are deployed to constrain the interference. Then there is the issue of snake oil claims when the subject is not understood.

It isn't just atmospheric interference that is the problem. Power supplies in equipment produce interference that really should be shielded. Some manufacturers acknowledge the problem and go so far as to place power supplies in separate cases. Others designed the layout so a partition can be utilized while others cram components as tightly as possible as if interference isn't an issue.

In the end, a near perfect frequency response with a low noise level just isn't enough to reproduce a realistic listening experience.

 

[mansr]

Wow, that analogue "signal" even goes backwards in time in some places. I wonder what that sounds like.