What can cause ground loops?

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romanianreaper

romanianreaper

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I'm occasionally getting noise with my 5150-III and feel like it could be the effects loop but still can't figure it out. Today I swapped out the speaker cable and felt like it made a difference with the noise but I could be imagining it.

I get this sound that is a slight "whir, whir, whir" and when I touch the strings, the noise increases. I know the 5150-III is a noisy amp but on the clean channel, I don't feel like I should be getting that level of noise.

I can live with the noise but drives me crazy. Maybe it is my house wiring? Is there a reason the noise would be worse with just the effects loop? Does that automatically mean the problem is in the effects loop or can that just be the thing increasing rhe issue?
 
If the noise is consistently worse with the loop, then it's either the loop itself or what's being placed in the loop. A ground loop is usually a hum, not a whirring sound but try the below:

- Try engaging the loop with just a patch cord linking in and out jacks - if that sounds clean (and it should), then the problem is with your external gear.
- Once you've done the obvious like try one pedal at a time and swap out leads, try running just one pedal off its battery. If that's clean, then you likely have an FX power supply issue or a ground loop.

Try it out and report back.
 
Behringer makes this ground loop eliminator that is a good 20 investment but yeah a ground loop is like a consistent high pitch tone.
 
@romanianreaper hey man what’s your whole signal path?

A ground loop usually occurs when two powered, separately grounded devices connect in a signal chain and so are made to share a ground.

This can’t be cured by improving the quality of your cables. You’ll have to break the ground loop either by lifting (disconnecting) the grounding of one of the devices in the chain, or by separating the grounding of the devices by inserting an isolation transformer device between the line or instrument level signal lines that connect the two devices.

I bought a few of these iso transformers on Amazon a while back. They’re cheap and small, and as long as they’re used with a buffered signal, absolutely transparent sounding.

However, ground loop noise is pretty consistent. If the noise changes intensity or tone depending on what you do with your guitar, it’s probably not a ground loop. If the sound is a whirring that oscillates, it’s likely not a ground loop. Again though, if it is the power at your house, you can get a power conditioner for your amp. That’s going to be more expensive than a simple iso transformer for a line level signal but it will isolate your rig from noisy power.

One caveat I’ll mention is this… when you see hoof prints, start by thinking horses, not zebras. Do you have any unshielded cables in your rig? Are you getting this noise with all your guitars? Humbucker vs single coil?
 
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TheGreatGreen said:
I bought a few of these iso transformers on Amazon a whole back. They’re cheap and small, and as long as they’re used with a buffered signal, absolutely transparent sounding.
Click to expand...
The BOJACK EI-14 ones ?
 
PLX said:
The BOJACK EI-14 ones ?
Click to expand...

I’ve bought ones from Pyle and Behringer. I don’t really notice a difference in sound or function between the two. They both work great.
 
TheGreatGreen said:
@romanianreaper hey man what’s your whole signal path?

A ground loop usually occurs when two powered, separately grounded devices connect in a signal chain and so are made to share a ground.

This can’t be cured by improving the quality of your cables. You’ll have to break the ground loop either by lifting (disconnecting) the grounding of one of the devices in the chain, or by separating the grounding of the devices by inserting an isolation transformer device between the line or instrument level signal lines that connect the two devices.

I bought a few of these iso transformers on Amazon a while back. They’re cheap and small, and as long as they’re used with a buffered signal, absolutely transparent sounding.

However, ground loop noise is pretty consistent. If the noise changes intensity or tone depending on what you do with your guitar, it’s probably not a ground loop. If the sound is a whirring that oscillates, it’s likely not a ground loop. Again though, if it is the power at your house, you can get a power conditioner for your amp. That’s going to be more expensive than a simple iso transformer for a line level signal but it will isolate your rig from noisy power.

One caveat I’ll mention is this… when you see hoof prints, start by thinking horses, not zebras. Do you have any unshielded cables in your rig? Are you getting this noise with all your guitars? Humbucker vs single coil?
Click to expand...
Thanks man! Yeah I go guitar into a pedalboard and have a noise gate but only for the in/out, not effects loop. The effects loop has a reverb pedal, delay, and clean boost in it.
 
ZEN Amps said:
If the noise is consistently worse with the loop, then it's either the loop itself or what's being placed in the loop. A ground loop is usually a hum, not a whirring sound but try the below:

- Try engaging the loop with just a patch cord linking in and out jacks - if that sounds clean (and it should), then the problem is with your external gear.
- Once you've done the obvious like try one pedal at a time and swap out leads, try running just one pedal off its battery. If that's clean, then you likely have an FX power supply issue or a ground loop.

Try it out and report back.
Click to expand...
Thanks!! I think I did the patch cable trick once before but I'll fo it again just in case. If I remember right, the noise didn't go away.
 
romanianreaper said:
Thanks man! Yeah I go guitar into a pedalboard and have a noise gate but only for the in/out, not effects loop. The effects loop has a reverb pedal, delay, and clean boost in it.
Click to expand...

How are you powering your amp and each of those pedals?
 
I had major ground noise in my Studio (bedroom.. :ROFLMAO:) and it tuned out to be a defective power cord with a broken Ground to my left Monitor. I had that going on for YEARS.. I thought it was my Computer but the Computer just exacerbated the noise..

Check everything..
 
midnightlaundry said:
I had major ground noise in my Studio (bedroom.. :ROFLMAO:) and it tuned out to be a defective power cord with a broken Ground to my left Monitor. I had that going on for YEARS.. I thought it was my Computer but the Computer just exacerbated the noise..

Check everything..
Click to expand...
Holy crap, that sucks! Lol. Wow that is like those stories where someone goes their everything and then their guitar wasn't plugged in. ?
 
Literally just went thru this…it was my pickup. I bumped it a little and it’s fine now. Hopefully I’ll get to fix it for real soon

Try a different guitar and see. I went thru the loop and a few other things. Once I figured it’s the guitar I was worried bad microphonic pickup. Best I can tell it’s a slightly bad connection with the bridge HB

I almost bought a fancy power strip and such to get rid of it
 
"Whir-whir-whir" isn´t a ground loop, those sound like hummmmmm. What you have there is outside interference from something. But the thing is, the fact that it increases when you touch the strings means your grounding isn't working like it should. Your body acts like a big antenna for stray interference in the room, and normally that noise goes away when you ground yourself via the strings or anything connected to ground on the guitar... the knobs, bridge, output jack and so on. Dumping the noise you've gathered to ground, basically. You are apparently just focusing it to the electronics instead.
 
Dave L said:
"Whir-whir-whir" isn´t a ground loop, those sound like hummmmmm. What you have there is outside interference from something. But the thing is, the fact that it increases when you touch the strings means your grounding isn't working like it should. Your body acts like a big antenna for stray interference in the room, and normally that noise goes away when you ground yourself via the strings or anything connected to ground on the guitar... the knobs, bridge, output jack and so on. Dumping the noise you've gathered to ground, basically. You are apparently just focusing it to the electronics instead.
Click to expand...
a noisy pedal/power supply or dirty power to the amp was the first thing that came to mind based on the description, or like some appliance sharing the circuit.

you run an extension cord from an outlet somewhere else in the house to just the amp / no pedalboard, and process of elimination.
are you plugging your amp and pedalboard power supply(s) into the same multi-outlet, etc?
bad tube? i've had rumbly wind type noise from a bad 12ax7 recently.
 
Moral of the story is almost anything within a guitar rig, nearby a guitar rig (eg. large transformers, certain appliances) or dirty power can cause erratic noise, hum, buzz, interference, etc.
 
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