Question Speakers Buzz when New PC is Off

[drambit]

My speaker setup is two Micca desktop speakers connected to a switch I made (just switches from headphones to desktop speakers, there's no ground loop,) connected to a stereo amp, connected to motherboard audio.

Motherboard: Asus B550M-A Wifi II.

Everything works fine when the PC is on, but as soon as the PC either goes to sleep or turns off, the speakers start loudly buzzing.

Note: Both PC and speakers are all plugged into the same power bar.

I did not experience this problem at all with my previous PC. when everything was exactly the same except for the case, motherboard, and PSU.

Any ideas on what might be going wrong?

 

[Ralston18]

When the PC is off and speakers are buzzing start disconnecting cables serving the PC. Leave the power cable for last.

Unplug the cables one at a time allowing some time between unplugs.

Determine if a particular cable stops the buzz.

You may have to go back and "do-over" using a different unplugging sequence.

I would also doublecheck all audio connections - especially within the new case.

Figure out how to test without the power bar and the switch.

 

[DaleH]

My speaker setup is two Micca desktop speakers connected to a switch I made (just switches from headphones to desktop speakers, there's no ground loop,) connected to a stereo amp, connected to motherboard audio.

Motherboard: Asus B550M-A Wifi II.

Everything works fine when the PC is on, but as soon as the PC either goes to sleep or turns off, the speakers start loudly buzzing.

Note: Both PC and speakers are all plugged into the same power bar.

I did not experience this problem at all with my previous PC. when everything was exactly the same except for the case, motherboard, and PSU.

Any ideas on what might be going wrong?

I'd guess it's related to what you did with the switches. The sound is indicative of a ground problem (open) and probably related to what you just did.

 

[drambit]

When the PC is off and speakers are buzzing start disconnecting cables serving the PC. Leave the power cable for last.

Unplug the cables one at a time allowing some time between unplugs.

Determine if a particular cable stops the buzz.

You may have to go back and "do-over" using a different unplugging sequence.

I would also doublecheck all audio connections - especially within the new case.

Figure out how to test without the power bar and the switch.

I'd guess it's related to what you did with the switches. The sound is indicative of a ground problem (open) and probably related to what you just did.

I did a bunch of testing just now.

Results:

• Unplugging all other cables from the PC, including the power cable, did not stop the buzz. Unplugging the power cable does change the sound of the buzz significantly.
• Bypassing the switch completely, so that the speaker amplifier is plugged directly into the motherboard 3.55 mm audio jack, also does not stop the buzz.
• Unplugging everything else from the power bar did not stop the buzz.
• Technically, turning on the PC does not stop the buzz either, it remains through POST. The buzz only seems to go away once I hit the Windows login screen (or about 1-2 seconds before that.)

Reminder that I have no good reason to suspect the power bar, wall sockets, speakers, speaker amps, any of the devices plugged into the PC, or any of the other devices plugged into that power bar, as this problem did not exist at all with my previous PC one week ago, regardless of whether the PC was off or on.

Also note that this is a rear panel audio jack, so the tightness of audio cables inside the PC or lackthereof should not be a factor in my opinion, though I did double check the cables and all of them are good and tight.

Any other ideas? Wonky grounding on the I/O panel or something?

 

[Ralston18]

Also try to locate the specific source of the sound/buzz. Use a cardboard tube or rolled up sheet of paper to listen around inside the case. Hold one end of tube to your ear and carefully aim the other tube end towards potential sound locations. Does the motherboard have a speaker?

= = = =

Could be some TR, TRS, TRSS mismatch.

FYI:

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

And also, per @DaleH take another look at that switch.

If the sound does not stop when PC power is unplugged then power must be coming in via an audio connection. Or even video.

Sketch out an electrical diagram showing all connections, ports, devices, outlets, power bars, etc.. Include front panel connections.

Down to individual wires and pins.

Post the diagram. Someone may spot something amiss.

Likely there is still some path into the PC when the power cord is unplugged.

Find that path - check the switch again. Use a bright flashlight to examine the I/O panel inside and out.

Regarding Windows: Right click the small speaker icon usually located in the lower right screen corner.

A menu should appear with multiple audio related choices. Work through the various menus, tabs, and properties. Just explore first to determine if there is something not as it should be or otherwise unexpected.

 

[drambit]

If the sound does not stop when PC power is unplugged then power must be coming in via an audio connection. Or even video.

The source of the buzz is just the speakers themselves, the noise does not come from the PC. It persists when everything else in the entire PC is unplugged except just the stereo audio jack from the rear motherboard. It persists yet when the PC power cable and the power cable for both monitors are all unplugged from the power bar.

So, in its most simplified setup, my PC is plugged in only with power cable, there is a 3.5mm stereo jack going from the back of the motherboard to my SMSL SA-50 Stereo Audio Amplifier via 3.5mm to dual RCA, then from that amplifier via banana plugs to my two speakers.

Other notes:

• It is significantly quieter but still present if I remove an extension cord from the mix. Here's a picture of the dual 3.5mm 3 ring to single 4 ring 3.5mm extension cable:

• Unplugging the power cable from the PC makes the noise much louder.
• Unplugging the audio cable from the PC and touching it makes it very loud
• With the audio cable plugged in, touching the I/O shield with my finger changed the sound.
• The grounds on the I/O shield all look to be touching normally.
• The sound goes away when the PC is on.

Questions:

1. Is it normal for speakers to buzz when the audio jack is in the air?
2. Why one earth would the sound go away when the PC is on?

 

[Deleted member 2947362]

Could just be down to a dodgy connection somewhere or you need better/higher quality cables.

This is a different scenario I know but when my mates hire a hall or somewhere just to have a jam all their audio buzzing problems mostly ended up being either cheap cables or bad connection so maybe it just the cables or a dodgy connection/connector somewhere in your setup.

It could even be down to how the amp/s are wired internally depending on the type and design.

 

[drambit]

Could just be down to a dodgy connection somewhere or you need better/higher quality cables.

This is a different scenario I know but when my mates hire a hall or somewhere just to have a jam all their audio buzzing problems mostly ended up being either cheap cables or bad connection so maybe it just the cables or a dodgy connection/connector somewhere in your setup.

It could even be down to how the amp/s are wired internally depending on the type and design.

The thing is, why would this never happen in my previous pc with all of the same cables and amps?

 

[ex_bubblehead]

This is classic ground loop. The speakers, extension cable and motherboard play a part here as evidenced by the fact that you have said that the hum is significantly reduced by removing the extension. If the only change was the motherboard then you've found the cause. You might be able to reduce/eliminate by using a ground isolator in line with the speakers to break the loop.

 

[Deleted member 2947362]

The thing is, why would this never happen in my previous pc with all of the same cables and amps?

That I cant answer for sure maybe the way your last system built by design?

But I still suspect it's either cables or something linked to the amp.

The buzz could be the amp/s picking up it's own PSU due to the way the earthing is routed between stuff ? I don't know?

But it sounds more like a bad connection or connector somewhere to me.


(nearly burnt my pizza hah not this time though lol)

 

[Ralston18]

Ground loop - time for that sketch.

Examples:

https://hackaday.com/2017/03/09/wtf-are-ground-loops/

https://www.w8ji.com/ground_loops.htm

 

[DaleH]

The source of the buzz is just the speakers themselves, the noise does not come from the PC. It persists when everything else in the entire PC is unplugged except just the stereo audio jack from the rear motherboard. It persists yet when the PC power cable and the power cable for both monitors are all unplugged from the power bar.

So, in its most simplified setup, my PC is plugged in only with power cable, there is a 3.5mm stereo jack going from the back of the motherboard to my SMSL SA-50 Stereo Audio Amplifier via 3.5mm to dual RCA, then from that amplifier via banana plugs to my two speakers.

Other notes:

• It is significantly quieter but still present if I remove an extension cord from the mix. Here's a picture of the dual 3.5mm 3 ring to single 4 ring 3.5mm extension cable:

• Unplugging the power cable from the PC makes the noise much louder.
• Unplugging the audio cable from the PC and touching it makes it very loud
• With the audio cable plugged in, touching the I/O shield with my finger changed the sound.
• The grounds on the I/O shield all look to be touching normally.
• The sound goes away when the PC is on.

Questions:

1. Is it normal for speakers to buzz when the audio jack is in the air?
2. Why one earth would the sound go away when the PC is on?

Still sounds like a ground, but it could be your ampllifier. Try another audio source other than the amplifier to see if that makes a difference.

 

[DaleH]

Still sounds like a ground, but it could be your ampllifier. Try another audio source other than the amplifier to see if that makes a difference.

Are all the AC connections of the three prong type? With the round pin being ground of course.

 

[Deleted member 2947362]

I know this different but unless they are using some high powered valve amps lol

but buzzing is normally a bad connection or connector and humming is most likely earth, cheap long leads wires or poor shielding can act as an transmitter and/or receiver.

 

[DaleH]

Are all the AC connections of the three prong type? With the round pin being ground of course.

With an ohmmeter, one can check the ground. On the micro connectors that plug into your computer, the top ring above the tip is ground. With power disconnected from the wall outlet for both your computer and the amplifier, check the resistance from the ground pin on the AC connector to the ground ring on your microconnector. It should read 0 ohms.

 

[drambit]

This is classic ground loop. The speakers, extension cable and motherboard play a part here as evidenced by the fact that you have said that the hum is significantly reduced by removing the extension. If the only change was the motherboard then you've found the cause. You might be able to reduce/eliminate by using a ground isolator in line with the speakers to break the loop.

The cause just being a badly designed motherboard? If so, then why would it not buzz when the computer is on?

Are all the AC connections of the three prong type? With the round pin being ground of course.

Yes they are.

With an ohmmeter, one can check the ground. On the micro connectors that plug into your computer, the top ring above the tip is ground. With power disconnected from the wall outlet for both your computer and the amplifier, check the resistance from the ground pin on the AC connector to the ground ring on your microconnector. It should read 0 ohms.

This is confusing in the way it's written. Which things should be unplugged and which connector's sockets should I be measuring resistance across?

 

[DaleH]

The cause just being a badly designed motherboard? If so, then why would it not buzz when the computer is on?

Yes they are.

This is confusing in the way it's written. Which things should be unplugged and which connector's sockets should I be measuring resistance across?

I agree. Kind of hard to explain in a text message, and not knowing your familiarity with DVM usage.

 

[drambit]

I agree. Kind of hard to explain in a text message, and not knowing your familiarity with DVM usage.

I use them all the time. It's just not clear which things you are referring to. "check the resistance from the ground pin on the AC connector to the ground ring on your microconnector. It should read 0 ohms." Is this the power cable plugged into the wall? The socket in the PSU? The Amp? Is the audio cable plugged into the PC but not the speakers? Plugged into the amp but not the PC? What are you asking?

 

[DaleH]

I use them all the time. It's just not clear which things you are referring to. "check the resistance from the ground pin on the AC connector to the ground ring on your microconnector. It should read 0 ohms." Is this the power cable plugged into the wall? The socket in the PSU? The Amp? Is the audio cable plugged into the PC but not the speakers? Plugged into the amp but not the PC? What are you asking?

Ok. On the theory that this is a ground problem, I would disconnect the AC power from your amplifier but have the the output of it plugged in to the computer. Then from the disconnected AC connector ground pin, measure the resistance from this pin to the chassis of the computer (it's power should still be connected). It may be hard to draw conclusions from this test. I had a similar problem with my son's amp, and it was just a few ohms above ground. Using a clip lead to jumper from one ground to another ground may be instructive. Good luck.