Question [solved] Speakers make noise only when connected to monitor audio output

Jan 4, 2022
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Setup:
- plugged into a single outlet via a power strip are:
- 1 PC
- monitor #1, connected to that PC
- monitor #2, NOT connected to PC in any way (other than sharing a power outlet)
- 2 speakers (sharing one power cable and audio cable)

When the speakers are connected to the audio output of my PC (via a 3.5mm jack), they are totally silent when no sound is playing. They are also silent when plugged into a laptop that's sitting on my desk.

But when I connect the same speakers' audio cable to the audio output of monitor #2 and switch them on, a deep but loud noise can be heared coming from the speakers.

What I tried so far:
  • It does not matter whether monitor #2 is turned on or off. It doesn't event matter whether monitor #2 is powered at all. Right now that monitor is completely switched off and the only cable connected to it goes directly to the speakers. Although the noise is more intense when the monitor is powered as well. (see screenshots)
  • I tried connecting the speakers to a different power outlet than everything else. Same outcome.
  • I tried unplugging the speakers from the monitor, keeping the cable in the same position, and instead connecting them to my mobile phone. I thought that maybe the cable's position somehow caused the noise. But with that setup, no noise was heard and they worked fine. Switching back to the monitor, the noise came back instantly.
  • I tried all of these with actual music playing, and the music was just barely audible behind all that noise.
  • I also used some headphones, connected them to the monitor's audio output instead, and there was no noise at all. Music playing could be heard without problem.
Pictures:
1. Overview of complete setup with monitors #1 and #2, PC, speakers, two outlets, and one extension cord. Including:
- dark blue power cables
- light blue audio cable
- (grey video cable)
- red cable is the speakers' power cable when I tried a different outlet
- red cross is when I tried to disconnect monitor #2 from power altogether

Image: View: https://i.imgur.com/2CXe4Us.png


2. Screenshot of Spectroid app, when monitor #2 is powered.

Image: View: https://i.imgur.com/OlTpmPo.png


3. Screenshot of Spectroid app, when monitor #2 is not powered.

Image: View: https://i.imgur.com/2CFfDCW.png


To reiterate, the simplest setup where the noise occurs is:
  • Speakers plugged into power outlet and switched on,
  • speakers connected via audio cable to monitor,
  • that monitor not connected to anything else, not even the power supply.
And again, the speakers work just fine when connected to the PC or a laptop.

Thanks in advance for anyone who can point me in the right direction!
 
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Jan 4, 2022
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Audio ground loop?
https://www.sounddevices.com/tackling-ground-loop-audio-noise/
https://www.thebroadcastbridge.com/content/entry/11485/getting-rid-of-audio-ground-loops

Not seeing it your diagrams per se.

However add in monitor video cables. Monitor #1 being the grey line. Monitor #2 = ?
Thanks for the quick answer.

As far as I understand it, an audio ground loop can only occur when using different outlets. The noise also happens when everything is plugged into the same one.

As for monitor #2 video cable, I should maybe have left the first monitor part out of my description.

The plan is to uncouple monitor #2 from the whole setup, put it in a different part of the room, and use a Chromecast to get video and audio in there. Both work fine per se, thus monitor #2 does not need any direct connection to the PC. I can already play videos on and hear music from monitor #2. The problem is that it's very quiet compared to the loud noise the speakers are making - but only the speakers (e.g. not my headphones plugged into the same output), and only on that monitor (e.g. the speakers work fine when connecting them to the PC.
 

Ralston18

Titan
Moderator
I will need to defer to the audio engineering community regarding the power strip's possible involvement.

Not sure of how far "different outlets" applies.

In the meantime try some experiments with connections that do not involve the power strip. Or limits its' involvement with regards to any potential loop.

Just as a matter of elimination.

= = = =

Late thought: "a deep but loud noise can be heared coming from the speakers. "

Can you record the actual sound and post the video? Someone may be able to specifically identify the source or cause of the sound.
 
Jan 4, 2022
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I will need to defer to the audio engineering community regarding the power strip's possible involvement.

Not sure of how far "different outlets" applies.

In the meantime try some experiments with connections that do not involve the power strip. Or limits its' involvement with regards to any potential loop.

Just as a matter of elimination.

= = = =

Late thought: "a deep but loud noise can be heared coming from the speakers. "

Can you record the actual sound and post the video? Someone may be able to specifically identify the source or cause of the sound.
I have one recording of the sound. This is: "Speakers on, low volume -> unplugged from monitor (you can hear just a low hum coming from outside) -> plugged in again"

https://soundcloud.com/user-888253327%2Fnoise-unplugged-pluggedin View: https://soundcloud.com/user-888253327/noise-unplugged-pluggedin


I will also try to use the completely separate outlets, having only monitor#2 and the speakers plugged into each of them, or just these two into one outlet.

edit: had the privacy set to "private" on that clip, it's public now.
 

Ralston18

Titan
Moderator
I hear some pops and crackles and a distinct hum all along that 14 second soundcloud audio clip. With more continuing noises are after the 9 - 10 second mark.

One click sounds to me as if a mic or something else being turned on.

However, the audio continues beyond that 14 second mark with a person singing solo. Then the audio goes on into a band with a faster beat etc...

Noted some reference to Inge? Could be some Soundcloud "addin" tacked to your clip - do not know.

Is is possible for you to also obtain and test a couple of isolators - just to help troubleshoot?

And perhaps some audiophile members will read your post and provide additional thoughts and suggestions. I have no problem with that.
 
Jan 4, 2022
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I hear some pops and crackles and a distinct hum all along that 14 second soundcloud audio clip. With more continuing noises are after the 9 - 10 second mark.

One click sounds to me as if a mic or something else being turned on.

However, the audio continues beyond that 14 second mark with a person singing solo. Then the audio goes on into a band with a faster beat etc...

Noted some reference to Inge? Could be some Soundcloud "addin" tacked to your clip - do not know.

Is is possible for you to also obtain and test a couple of isolators - just to help troubleshoot?

And perhaps some audiophile members will read your post and provide additional thoughts and suggestions. I have no problem with that.
What you are hearing is described in this image:

View: https://i.imgur.com/4WsWrPT.png


About 5 seconds of the problematic noise, followed by me unplugging the jack from the monitor, followed by 3.5 seconds of ambient hum, followed by crackles as I plugg the audio cable into the monitor again, followed by another 3 seconds of the noise I'm concerned about. Remember - I don't know much about acoustics - but this is the test where monitor #2 is not connected to anything else, not even a power source. So I have only this: Outlet -> speakers -> monitor.

I can't vouch for some person singing after this, it would definitely not be the noise I'm talking about ;)


Isolators: Are you talking about these kind of things? https://audac.eu/Products/d/tr2070---stereo-groundloop-isolator-3-5mm-jack-male---3-5-jack-female

I still have to try the approach of completely separating monitor #2 and the speakers from everything else. Will get back with the results.
 
Jan 4, 2022
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Tried the most simple setup, and I still get that noise:

  • power strip to to single outlet (a third one, not either one of the two before)
  • power cable (dark blue) from power strip to monitor
  • power cable (dark blue) from power strip to speakers
  • audio cable (light blue) from speakers to monitor
View: https://i.imgur.com/oDxMlVw.png


I also still get the noise when the power cable to the monitor is not connected (red cross) or when I switch the speakers' power cable to a different outlet (red line).

I have not gotten the opportunity yet to test an audio isolator.

Edit: The monitor in question is the U28E590D by Samsung. Google shows me there were others in the past with a similar problem, but I have not found a solution there either.

Edit 2: Don't know if it's relevant, but the volume of that noise correlates to the volume level of my speakers. So I can turn the volume up and down and that changes the volume of the noise.
 
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Ralston18

Titan
Moderator
Speaker cables (TR, TRS, TRRS).

FYI:

https://www.cablechick.com.au/blog/understanding-trrs-and-audio-jacks/

I am, rightly or wrongly, still thinking a loop.

Here is another link with additional explanation:

https://www.techhive.com/article/3063590/how-to-get-rid-of-hum-and-eliminate-other-noises-from-your-audio-and-video-systems.html

The link provides other information and ideas that may lead you to a "Eureka" moment....

Are you able to physically swap the monitors? Or to substitute in another known working (no hum) monitor to test Monitor 1 and Monitor 2 in turn?

Yes that is the sort of isolator that I have in mind.

Key is to first discover the loop and if could be that the loop can simply be "broken" in some manner.

If breaking the loop is not viable - then try the applicable isolator.

(Caveat being that there is indeed a loop.... I have no problem with that being proven wrong. Objective is to identify the cause of the noise from the speakers.)
 
Jan 4, 2022
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Update: I found a working solution, and the noise is now kept at a very small minimum, which is just barely audible.

I tried some kind of self-isolating extension cord first, which would have been the easiest solution. But as it turned out that had no impact at all.

Then I tried an isolator along the audio cable line, which turned down the noise just by a little bit. Still, that was far from satisfying.

Then I introduced another component, an HDMI audio extractor, taking HDMI video+audio as input and having separate HDMI video and aux audio outputs. This finally got me to an acceptable level of noise, where I now only have to tune the source a little louder and the speakers a little down to no longer hear any of that.

View: https://i.imgur.com/x1KL7ae.png


Thanks for your help, because even though the solution was something else I learned a lot :)
 

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