Digital audio signal is interrupted by electrical interference coming from PC... even when powered off

[rorythedawg]

So I have isolated the buzzing coming through my headphones to my PC. It is an electrical buzzing and it is not stemming from any of my sound equipment, it is electrical interference with the signal going over USB to my audio setup. 

It does not happen when the USB cable is plugged into my laptop, but it does happen when its plugged into my PC via any USB port, it also happens when the PC is powered off (PSU off, drained caps, and literally unplugged)

It also happens when the USB is plugged into my monitor, i cant use my audio setup through the monitor but the electrical buzz can be heard when its plugged into it.

When i boot into a game the buzzing gets louder and more erratic so its definitely electrical interference on the digital signal. 

 

I dont know wtf is going on and im loosing my shit over it, plz help. Ill take any recommendations at this point.

[bmx6454]

did you try with psu off, and all devices disconnected except headset?

[rorythedawg]

12 minutes ago, bmx6454 said:

did you try with psu off, and all devices disconnected except headset?

i have tried with PSU off, caps drained (by holding power button while PSU is off) and computer literally unplugged. Ill try removing the rest of my i/o and see if i get a different result but I doubt it.

 

Update: still get it with only the USB cable plugged in for i/o

[bmx6454]

Just now, rorythedawg said:

i have tried with PSU off, caps drained (by holding power button while PSU is off) and computer literally unplugged. Ill try removing the rest of my i/o and see if i get a different result but I doubt it.

okay, then don't try lol

[rorythedawg]

25 minutes ago, bmx6454 said:

okay, then don't try lol

bruh i was just posting before i tried

 

26 minutes ago, rorythedawg said:

i have tried with PSU off, caps drained (by holding power button while PSU is off) and computer literally unplugged. Ill try removing the rest of my i/o and see if i get a different result but I doubt it.

 

Update: still get it with only the USB cable plugged in for i/o

 

[HenrySalayne]

I'm assuming you are connecting external equipment to your USB device (loudspeakers for example)? If you are, it is not your computer, but the additional ground loop through your computer. Disconnect anything but your headphones and try again. Then reconnect one piece of equipment after the other and check which is causing the problem. Use a line isolator or a ground lift on the device responsible.

[rorythedawg]

On 6/29/2020 at 4:40 AM, HenrySalayne said:

I'm assuming you are connecting external equipment to your USB device (loudspeakers for example)? If you are, it is not your computer, but the additional ground loop through your computer. Disconnect anything but your headphones and try again. Then reconnect one piece of equipment after the other and check which is causing the problem. Use a line isolator or a ground lift on the device responsible.

Yeah I have my audio running through an FX Audio Dac X6 into my AVR then into my headphones/speakers. 
Thing is If i just switch the input USB from my desktop to my laptop the sound is completely gone with no other changes to the setup. Leading me to believe it is stemming from the PC itself rather than from somewhere else in the setup. 

 

My next thought is to maybe get a USB expansion card to see if the PCIe lanes will help isolate the noise, though with my current mobo i need that slot for a wifi card until i move into my new place next month. 

Im not sure what you mean by "additional ground loop through my computer" though so you still may be correct.

My next guess as the issue would be the DAC as its a little older at this point and it was having issues with the amp side (just with some very low and high frequencies), Ill have to wait until I can use my roommates DAC next month to see for sure though. 

Update: If I turn my DAC off with the USB plugged in I can still hear the noise. 
If I use the bluetooth on my AVR for audio I dont hear the buzz, I do hear some stuff if i turn it up all the way, but its not the same and sounds more like a hissing, I think that can be chalked up to the bluetooth connection though. So I still think its the PC that is causing the issue. Though ultimately I dont know enough about all this to say for certain. Im also not sure what else I can do to test my other equipment as the only analog input for my AVR I have access to at the moment is my DAC x6. 

[akio123008]

What about the monitor? That may cause the interference as it's connected to the PC and you may not have unplugged it during the test. 

 

I have two monitors that produce audible noise on FM radio so it wouldn't surprise me.

[rorythedawg]

4 hours ago, akio123008 said:

What about the monitor? That may cause the interference as it's connected to the PC and you may not have unplugged it during the test. 

 

I have two monitors that produce audible noise on FM radio so it wouldn't surprise me.

Unfortunately not the monitors either.

I've tested it with everything unplugged from the computer apart from the audio USB cable. Ive also tried another cable. 

 

The thing that really confuses me is that I can hear it if i turn the PC off and the PSU off, and drain the mobo caps by holding the power button for 10 secs two times in a row. 

[HenrySalayne]

Do you hear the noise if nothing is connected to your USB audio interface but your headphones?

Most equipment using a power chord is grounded (3 pin plug; for safety reasons, do not disconnect the ground pin). You computer is also grounded just by pluging the cable into it even if the power switch is in the off position. Your monitor should be grounded as well and is connected to your computer ground potential.

But you need two devices plugged into a power outlet for a ground loop. So your amplifier or loudspeakers are likely the cause. Just unplug these and try again.

[rorythedawg]

7 hours ago, HenrySalayne said:

Do you hear the noise if nothing is connected to your USB audio interface but your headphones?

Most equipment using a power chord is grounded (3 pin plug; for safety reasons, do not disconnect the ground pin). You computer is also grounded just by pluging the cable into it even if the power switch is in the off position. Your monitor should be grounded as well and is connected to your computer ground potential.

But you need two devices plugged into a power outlet for a ground loop. So your amplifier or loudspeakers are likely the cause. Just unplug these and try again.

Omg, you are genius lmao. You are 100% correct. 

 

If I have both my PC and Monitor unplugged the sound stops, but having either one plugged in causes the buzzing. I guess the loop is between my AVR and my monitor and PC.

 

So the next question is how do I get it to stop?

Im thinking if i plug into different circuits maybe that would fix it since they would be grounded to different physical locations?

Maybe this is also why I only noticed it when I moved back to my parents house temporarily between apartments as I must have had my stuff plugged into two separate circuits prior? 

 

I will test this out and report back. 

 

Also thank you so much for your help, this has been driving me nuts and I couldn't figure out what the heck could have been causing it, I didn't consider it could have been the power going to my monitor at all, since when I had the DP cable unplugged I could still hear it before. 

[rorythedawg]

1 hour ago, rorythedawg said:

Omg, you are genius lmao. You are 100% correct. 

 

If I have both my PC and Monitor unplugged the sound stops, but having either one plugged in causes the buzzing. I guess the loop is between my AVR and my monitor and PC.

 

So the next question is how do I get it to stop?

Im thinking if i plug into different circuits maybe that would fix it since they would be grounded to different physical locations?

Maybe this is also why I only noticed it when I moved back to my parents house temporarily between apartments as I must have had my stuff plugged into two separate circuits prior? 

 

I will test this out and report back. 

 

Also thank you so much for your help, this has been driving me nuts and I couldn't figure out what the heck could have been causing it, I didn't consider it could have been the power going to my monitor at all, since when I had the DP cable unplugged I could still hear it before. 

Ok, so plugging the AVR (whose plug does not have a ground pin) into a different circut with only the PC plugged in still gets the buzz, also still have the buzz if the PC is plugged into the alternate circuit and the AVR is plugged into original circuit. 

This is with the monitor unplugged in both scenarios. Unplugged the PC in both cases still results in the buzz stopping. 

 

It looks like something like this: https://www.amazon.com/Jensen-CI-2RR-IsoMax-Isolator-Jensen/dp/B00ASVWYCS a ground loop isolator would also solve my problem. But that is a fairly expensive solution, anyway I can do this for free or cheaper?

 

Edit: ok looks like that was just a really expensive one: https://www.amazon.com/Earthquake-Sound-GLI-200-Kleaner-Isolator/dp/B07Z5SKRMR/ref=sr_1_8?dchild=1&keywords=ground+loop+isolator&qid=1593803169&sr=8-8 looks like theres ones that are much more affordable.

 

Any suggestions on how cheep/expensive I should be looking at for these? I don't wanna spend too much but definitely want to get something that will fully fix my issue. 

 

Edit2: Looks like ground loop isolators can also reduce bass frequency output, this isnt a huge deal nessicarily since I almost never crank the bass on my AVR, but is this somthing I should worry about? I may start a new thread for ground loop isolators since this one is cluttered and for the diagnosis. 

[rorythedawg]

Ok, it was the coax TV cable in the basement that was causing the ground loop, i guess that is grounded separately than the House plugs. With that unplugged I have no issue!

 

only figured this out due to this random thread I found when looking into ground loop isolators! https://forums.stevehoffman.tv/threads/do-ground-loop-transformers-isolators-degrade-sound-quality.461707/

 

Shout out to @HenrySalayne for figuring out it was a ground loop!