A Different Kind Of Ground Buzz Problem

[Nox]

Hello everyone. I'm having annoying ground buzz problem that I can't figure out and I wanted to ask you about it.

It seems to be an ordinary grounding problem, but despite checking every possibility I could think of, I couldn't find the source of the problem. I've tried different guitar, different wall socket, different cable, different interface and the problem persisted. I've checked the grounding of the guitar, the grounding of the wall sockets etc. but all of them looking just fine.

As the video shows, the buzzing gradually diminishes when I move the jack close to the metal surface of any plugged-in device like metal case of interface, metal parts of pc or metal imac stand. I can't figure out what's causing the problem. I would be grateful if you could help me

 

[Speedskater]

Does it happen in different rooms or buildings?

 

[sq225917]

Smps on the interface?

 

[kyuu]

Sounds like mains hum. Probably have a ground loop going on or mains noise is getting coupled to your audio circuit somewhere in your setup.

Is the hum present when the cable that I assume is connecting the guitar to the interface is disconnected?

 

[Nox]

Thank you for your quick responses. I have been trying to solve this problem for almost 2 months.

@Speedskater
I have no chance to try in another building, but the same problem persists in all rooms in my house.

@sq225917
I don’t know what smps is but interface powered by usb.

@kyuu
I connected all devices (pc and studio monitors) to the same socket to avoid any ground loop. No humming noise when the cable is not plugged into the interface. I’ve tried five different cables but problem persisted.

 

[madrac]

Smps is switch mode power supply.

For whatever reason, video won’t play unless I sign in. Anyways, is buzz still there if you bypass the interface (eg plug directly into amp)?
Maybe some dc offset? Emotiva sells a power strip designed to eliminate this. Called the cmx2, I think

 

[Roland68]

Hello everyone. I'm having annoying ground buzz problem that I can't figure out and I wanted to ask you about it.

It seems to be an ordinary grounding problem, but despite checking every possibility I could think of, I couldn't find the source of the problem. I've tried different guitar, different wall socket, different cable, different interface and the problem persisted. I've checked the grounding of the guitar, the grounding of the wall sockets etc. but all of them looking just fine.

As the video shows, the buzzing gradually diminishes when I move the jack close to the metal surface of any plugged-in device like metal case of interface, metal parts of pc or metal imac stand. I can't figure out what's causing the problem. I would be grateful if you could help me

You should list everything you connected and how you connected it.

How did you check the grounding of the sockets?

Do you have a short cable, about 50cm or shorter, just for testing?

 

[Nox]

You should list everything you connected and how you connected it.

How did you check the grounding of the sockets?

Do you have a short cable, about 50cm or shorter, just for testing?

I connected just desktop pc (i also tried with an imac) and one yamaha hs8 studio monitor (I didn't even plug the display monitor) to same wall socket with simple multi plug outlet extender. I also tried it with power strip and extension cord, noting's changed.

I checked grounding of the sockets with a multimeter. I connected ground and neutral to the multimeter and got about 2V.

I don't have a short cable because instrument cables are not made that short but i think i can find a shorter guitar patch cable.

 

[SSS]

Sound is from mains coupled into the guitar cable. Looks like that the ring and thus the shielding is not grounded in the ADC jack. May be it is a floating input and there is perhaps a ground lift switch. Since I don't recognize the exact model I can't look into a manual in order to better understand the inputs. If there is a dedicated guitar (DI) input there this one needs to be used.

 

[JayGilb]

Who is the manufacturer and the model of your audio interface ?
It looks like some model of the Scarlett.

 

[Nox]

@SSS @JayGilb

Yes, it is a focusrite scarlett 2i4 1st gen. User Guide

 

[SSS]

Hm, no ground switch. Input function switches automatically when used XLR or guitar cable. Does the input 2 show the same behavior? If yes, may be that the scarlett has an internal failure?

 

[SSS]

One test more, does the buzz hum exist when you plug the guitar cable attached to the guitar into a regular guitar amplifier?

 

[Nox]

Hm, no ground switch. Input function switches automatically when used XLR or guitar cable. Does the input 2 show the same behavior? If yes, may be that the scarlett has an internal failure?

Yes, the 2nd input does the same thing. I don't have a guitar amplifier at the moment but I connected the guitar directly to the line input of my computer. The buzz is still there.

 

[JayGilb]

Were both interfaces tested usb powered ? Have you tried a different usb cable ?

 

[Nox]

Were both interfaces tested usb powered ? Have you tried a different usb cable ?

Yes, I tried different usb cables, unfortunately the problem persisted.

I also tried with a notebook to create a closed circuit. When I unplug the notebook and run it on the battery, the buzz stops, then starts again when I plug it in.

 

[JayGilb]

Yes, I tried different usb cables, unfortunately the problem persisted.

I also tried with a notebook to create a closed circuit. When I unplug the notebook and run it on the battery, the buzz stops, then starts again when I plug it in.

An usb isolator might help. They sell models that allow you to power the device from an additional power source.

 

[SSS]

Did you try a different guitar cable? Since problem persists at the notebook then I think the guitar cable is the problem. When the notebook is on battery only then there is no ground connection and the induced buzz is floating regarding the input (ring and pin have then the same buzz signal) and therefore not evident.

 

[AnalogSteph]

That's an odd problem. It almost seems like mains PE is disagreeing rather substantially with actual ground potential.

What happens if you run the laptop on battery but plug the (powered) HS8 into the interface? If that also buzzes, I'd strongly suspect that mains PE is not actually connected to a proper ground. Possibly the kind of outdated setup that just ties PE to neutral locally (not sure to which degree that is still up to code), or just faulty. An electrician may be able to shed more light on the matter then.

 

[JayGilb]

That's an odd problem. It almost seems like mains PE is disagreeing rather substantially with actual ground potential.

What happens if you run the laptop on battery but plug the (powered) HS8 into the interface? If that also buzzes, I'd strongly suspect that mains PE is not actually connected to a proper ground. Possibly the kind of outdated setup that just ties PE to neutral locally (not sure to which degree that is still up to code), or just faulty. An electrician may be able to shed more light on the matter then.

"I also tried with a notebook to create a closed circuit. When I unplug the notebook and run it on the battery, the buzz stops, then starts again when I plug it in."

That was mentioned by the OP a few comments above.