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sounding off - bad noises

Old 28th Jul 2020, 18:51
  #1 (permalink)  
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sounding off - bad noises

I am having some issues with the audio output from my favourite desktop computer. Normally, the sound out is very smooth and nice on the ear. When the machine is first turned on there is a bit of hiss and wooshing, not loud but noticeable, this goes away once the OS (Linux Mint 18.x) is up and running and noises from all applications and media players is good to listen to. This last few days I have found that the hiss and whoosh doesn't go away when the OS is established and on top of that there is an additional buzzing noise related to all movements of the mouse and keyboard actions. When listening to music via Youtube the sound quality has become very harsh and gritty, not at all nice to listen to.

The machine has not got any internal speakers, all of the sound is piped to a decent HiFi power amplifier and some good sized speakers.

My first thought is that I am having an issue with my graphics card, which has the sound output stuff associated with it. I have tried using an external sound card jobby that plugs into a USB socket, the sound issues are pretty much the same as the graphics card ones.

I don't know what to try next.



rans6andrew is offline  
Old 29th Jul 2020, 09:41
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How do you connect the keyboard and mouse? Hardwired or bluetooth/wireless? With the movements and actions from these intruding into your sound card, I suspect some kind of radio interference. Finding out where it is coming from might be a big job though. I would try swapping out whatever you can, cables, the amplifier, other peripherals, until you can narrow down where the noise is being generated.
Jhieminga is offline  
Old 29th Jul 2020, 09:57
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further investigation shows that the buzzing interference is only heard when something causes the screen picture to move/change. ie up or down scrolling but not sideways arrow keys that don't cause a change in the view.

Keyboard is wired, mouse is wireless, not sure what frequency. If unplugged at the sound output jack the noise goes away showing the amplifier to be quiet. I'll try a different sound source to see if the amp has gone a bit harsh but I doubt it is part of the problem.


rans6andrew is offline  
Old 29th Jul 2020, 18:55
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Check if there are cables close to your display cable, it might be interference between the display connection and your sound setup. You can also try unplugging the HDMI/Displayport/etc. cable and trying to scroll the page (you won't see it obviously). Or try a different connection to your monitor, or a different cable.
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Old 29th Jul 2020, 20:38
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The arrangement of the bench where the monitor sits above and the main box stands on the floor beneath doesn't leave any scope for cables to be routed anywhere else other than where they are (and have been for some years!) due to cable length limitations. Ditto keyboard. Wireless mouse is unchanged for a long time. The audio amp stands atop the floor standing PC box. If a completely different sound source (Android tablet) is plugged in using the same amp i/p and cable there is no issue with the sound quality or with the hiss/buzz effects reported yesterday. I have moved nothing knowingly over the weekend so I am still at a loss to figure out what is wrong.

Something inside the PC box is not happy.............

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Old 29th Jul 2020, 22:10
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Could be that the power supply is on the way out. Or else it could be a USB problem. Try uninstalling and reinstalling the USB root hub (works best with a PS2 mouse & keyboard).
Saab Dastard is offline  
Old 1st Aug 2020, 01:34
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Are you using Pulse Audio or ALSA? Either way, open up the appropriate mixer tool and try turning down any microphone levels slightly.

EEngr is offline  
Old 3rd Aug 2020, 20:56
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The hardware in the machine has neither speaker nor microphone. It is possible that there is a floating analogue input that may be picking up noise........... Nothing inside the box has been changed so I don't understand why strange noises are happening now that were not doing so before. I don't know whether Pulse Audio or ALSA are in use, possibly neither.
rans6andrew is offline  
Old 3rd Aug 2020, 21:33
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It could be your PSU is on its way out, sounds like an earthing issue which would usually be associated with one of the rails of the PSU not working properly.
andytug is offline  
Old 4th Aug 2020, 08:56
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Hmm, kind of doubt it's the PSU. These are as likely to give a direct whine when a capacitor or something is on the way out. So I reckon it's software. Safe boot to see if it's still there?
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Old 4th Aug 2020, 17:34
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The amp and speakers used for my desktop can also work with my Panasonic tv, although they do need to be moved to the tv.

I know you think the amp and speakers are innocent, as the noise is not present when they are disconnected from the pc. However, would it be worth setting them up with another source? Just in case?
Ancient Observer is offline  
Old 7th Aug 2020, 16:59
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Boot from a Linux CD and see if the problem is still there.

Mac (Mint fan)
Mac the Knife is offline  
Old 14th Aug 2020, 16:10
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I didn't have a lot of time to investigate the issue but I needed to get on with stuff so I swapped to another i7 machine running Linux Mint. Sound was good from the new machine using the same audio power amp but when I tried to install Zoom it went through the motions but it doesn't function, at all. Another issue to chase up!

Yesterday, I changed back to the old i7 machine running Linux Mint where Zoom does work but the sound was bad. I noticed that the wooshing and buzzing background noise was modulated by the movement of repositioning the machine under my bench. Further investigation shows that there are some screw heads slightly proud on the bottom of the amplifier which sits atop the computer box which have rubbed through the paint on the top of the box (amp has rubber feet but they are spaced wider than the top of the computer case) and are providing some sort of earth connection between the computer and the amp. The computer is powered from the mains with a 3 pin mains lead and has a solid earth to its case whereas the power amp is on a two core mains lead and must normally float with respect to mains earth. Obviously, there is an earth associated with the signal lead and the amp is grounded sufficiently to stop audible mains hum in normal use. It seems the the computer is not happy when its audio ground gets wired back to its case via the power amp chassis. Sliding a sheet of cardboard between the top of the computer and the base of the amp has solved the problem.

All is not sweetness and light, however. During a Zoom meeting last evening the machine lost much of the display, some windows on the screen stopped moving, some went black and only the sound carried on operating. The mouse pointer was still alive but nothing could be "clicked" and the keyboard was dead. The only influence I could have was by pressing the reset button. After rebooting it was all working as per normal for about 20 minutes and then it locked up again. There is something odd about Zoom and Linux Mint. All day yesterday up to the Zoom meeting and all day today the machine has been fine. I have been watching the steam trains operating from Grosmont on the NYMR, some Youtube videos and some BBC news videos and everything has been fine, no lock ups, no bad sound.

Thank you to all of those who made helpful suggestions regarding the noises issue, at least it was a no cost solution when we got there.

rans6andrew is offline  

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