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Magnetic Ether

Ground Loop Hum

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So I figured out that the hum I get whenever I try and record electric guitars comes from my laptop's power cord. Having learned this, I would just record from my battery, but it's so bad that it can only last a few minutes.

Just wondering if this plagues anyone else and if there's anything you do to get rid of/minimize it. I know there are things you can buy to eliminate it, but they're expensive...

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If the sound is only in the low end, I'd say EQ it out. If you're a male doing male vox, then lots of the bass should be taken out anyway. Bass and sometimes guitar and piano, on the other hand... I'd get that device Metal Man's talking about if it helps.

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A humming mostly means either your plug or your charger is not correctly grounded or there could be a problem with the power outlet as well (not very likely but possible, at least in Germany it can happen). I know those problems from car stereos.

But I don't get Metal Mans image :?

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As others have said, it is most likely a grounding issue. They have grounders you can buy and plug into the socket before you plug in your power cord that might help alleviate the hum.

It could also be your sound drivers. Laptops aren't usually fitted with great sound cards. If you're not using ASIO drivers, I'd recommending getting ASIO4all and running that. That could also get rid of the hum.

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Is your guitar pickup a double-coil humbucker (which is less prone to noise) or is it single-coil (which is more prone to noise)?

Have you tried plugging into a different outlet?

Alternately, have you priced a new laptop battery? Knowing laptop batteries, it would probably be more expensive that the ground hum reducing thing, but it might be worth checking.

Additionally, are you talking about using the ground hum reducer on the laptop plug or on a guitar amp plug? If on the laptop, is your laptop plug three-pronged? If it doesn't have that third grounding prong to begin with, the ground hum reducer is probably not going to do anything. Even if it is a grounded plug, the hum reducer may still not do anything because it may not be a laptop grounding issue -- it may just be electrical interference from the AC adapter that's messing with the guitar like you sometimes get from CRT monitors and florescent lights. There's a shielding thing you can do to the interior electronics-containing cavities of the guitar that's supposed to reduce this sort of interference, especially for single-coil pickups. If you're comfortable taking your guitar apart, you can get kits for this for ~$20 (e.g http://www.stewmac.com/shopby/product/3789).

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Is your guitar pickup a double-coil humbucker (which is less prone to noise) or is it single-coil (which is more prone to noise)?

Double.

Have you tried plugging into a different outlet?

Once or twice. Didn't seem to make a difference.

Alternately, have you priced a new laptop battery? Knowing laptop batteries, it would probably be more expensive that the ground hum reducing thing, but it might be worth checking.

Yeah, they're way too expensive. My battery wasn't even very good when I first got it either (Lasted maybe 2-3 hours and recording would just drain it faster). Ideally I'd like to be able to record while it's plugged in.

Additionally, are you talking about using the ground hum reducer on the laptop plug or on a guitar amp plug? If on the laptop, is your laptop plug three-pronged? If it doesn't have that third grounding prong to begin with, the ground hum reducer is probably not going to do anything. Even if it is a grounded plug, the hum reducer may still not do anything because it may not be a laptop grounding issue -- it may just be electrical interference from the AC adapter that's messing with the guitar like you sometimes get from CRT monitors and florescent lights. There's a shielding thing you can do to the interior electronics-containing cavities of the guitar that's supposed to reduce this sort of interference, especially for single-coil pickups. If you're comfortable taking your guitar apart, you can get kits for this for ~$20 (e.g http://www.stewmac.com/shopby/product/3789).

I would be using it on my laptop power cord. I record directly into my audio interface so there is no amp.

I don't think it's interference because the noise is there even when the guitar isn't plugged in and as soon as I unplug the power cord it goes away.

I was thinking about shielding for a while but I'm really not comfortable opening up the guitar. I may still do it in the future, but the noise coming from the guitar itself is usually quite minimal. I'm almost positive the issue is being caused by the laptop cord.

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I don't think it's interference because the noise is there even when the guitar isn't plugged in and as soon as I unplug the power cord it goes away.

Ah, I see. Another question, then: is the power to the audio interface provided by the USB connection or does the interface have its own AC adapter that plugs into the wall? My understanding is that USB-powered interfaces tend to have more of a problem with noise since the current supplied by USB is less consistent than you get from an AC adapter. I could see how having a bad connection from wall to computer -- especially on laptops, which aren't always great at powering USB devices in the first place -- could perhaps make any USB power issues even worse.

EDIT: If the interface is USB-powered, you could maybe try getting a powered USB hub that has its own AC adapter and running the interface from that so that the interface isn't getting its power supply through the computer's power cord.

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Ah, I see. Another question, then: is the power to the audio interface provided by the USB connection or does the interface have its own AC adapter that plugs into the wall? My understanding is that USB-powered interfaces tend to have more of a problem with noise since the current supplied by USB is less consistent than you get from an AC adapter. I could see how having a bad connection from wall to computer -- especially on laptops, which aren't always great at powering USB devices in the first place -- could perhaps make any USB power issues even worse.

EDIT: If the interface is USB-powered, you could maybe try getting a powered USB hub that has its own AC adapter and running the interface from that so that the interface isn't getting its power supply through the computer's power cord.

Yeah, it's usb powered.

As for your hub suggestion, I didn't even know something like that exists...could you show me exactly what you mean?

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So I figured out that the hum I get whenever I try and record electric guitars comes from my laptop's power cord. Having learned this, I would just record from my battery, but it's so bad that it can only last a few minutes.

Just wondering if this plagues anyone else and if there's anything you do to get rid of/minimize it. I know there are things you can buy to eliminate it, but they're expensive...

I mean you could try a ground lift... nahh.

Sometimes plugging everything to the same surge protected multi power outlet works for me when I get hum

maybe your gain is high or your recording near a tv

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Hey I know I could rent that Ebtech HumX from a local shop where they sell and rent stuff like speakers for small events. It was like 10$ for a few days and he would credit me the 10 bucks on the full purchase, you might as well look for such a shop. They fucking sold it 80$ tho.. I kept my hum :).

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Hey I know I could rent that Ebtech HumX from a local shop where they sell and rent stuff like speakers for small events. It was like 10$ for a few days and he would credit me the 10 bucks on the full purchase, you might as well look for such a shop. They fucking sold it 80$ tho.. I kept my hum :).

I've looked around, but none of the rental places here seem to rent accessories like that. If I can though, I would like to try it out first if I decide to buy it; I don't want to bring it home and find out that it doesn't fix the problem.

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Yeah, it's usb powered.

As for your hub suggestion, I didn't even know something like that exists...could you show me exactly what you mean?

Something like this.

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I've had a similar problem before. It wasn't a grounding issue though. Your laptop power supply is probably a switched mode power supply which means it kicks out a lot of magnetic noise. That means whenever your power supply is on the noise is inducted onto any unbalanced.

Before going to see if the problem is a grounding problem I would suggest trying a balanced cable first. Sine you're recording guitars I assume that you're just using a standard jack cable. You can get balanced jacks which don't cost much more than regular jack leads.

Hope this helps!

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Something like this.

That does sound like it might work. Uggh, so many options XD.

I've had a similar problem before. It wasn't a grounding issue though. Your laptop power supply is probably a switched mode power supply which means it kicks out a lot of magnetic noise. That means whenever your power supply is on the noise is inducted onto any unbalanced.

Before going to see if the problem is a grounding problem I would suggest trying a balanced cable first. Sine you're recording guitars I assume that you're just using a standard jack cable. You can get balanced jacks which don't cost much more than regular jack leads.

Hope this helps!

Okay, interesting...when you refer to balanced cables, you're talking about the guitar cable and not the laptop power cord yes?

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Okay, interesting...when you refer to balanced cables, you're talking about the guitar cable and not the laptop power cord yes?

Yeah the guitar cable. The noise might be being inducted onto other parts of the guitar though, like through the pickups so might not 100% solve the issue. Depending on what the guitar is it might not work with a balanced jack lead.

What guitar is it you're recording?

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Yeah the guitar cable. The noise might be being inducted onto other parts of the guitar though, like through the pickups so might not 100% solve the issue. Depending on what the guitar is it might not work with a balanced jack lead.

What guitar is it you're recording?

Just a shitty Epiphone Les Paul Special.

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Just a shitty Epiphone Les Paul Special.

Hmmm, I'm not sure if it'll work or not. Can't hurt to try! You could always return it if it doesn't work.

A quick solution would be to put your DC converter as far away from your laptop and guitar as possible, won't solve the problem but should make a slight difference.

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One other question. You say the hum goes away when you unplug the computer's power cord -- are you unplugging the power adapter from the wall with the adapter still plugged into the computer, or are you unplugging the power adapter from the computer with the adapter still plugged into the wall? Also, how is the power adapter constructed? Is it built into the computer, or is it a separate unit?

What I'm getting at is this: Is it the power adapter being plugged into the wall that's causing the hum, or is it the power adapter being plugged into the wall and connected to the computer that's causing it? If you can, try plugging the adapter into the wall but leaving it disconnected from the computer and see if the hum occurs. This may help determine whether the adapter is causing general electrical interference or whether it's an issue with the power feed that the adapter is supplying.

EDIT: While we're at it, with regard to the hum still being there when the guitar is unplugged: Is the cable for the guitar still plugged into the audio interface, or are all the input cables disconnected from the interface?

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One other question. You say the hum goes away when you unplug the computer's power cord -- are you unplugging the power adapter from the wall with the adapter still plugged into the computer, or are you unplugging the power adapter from the computer with the adapter still plugged into the wall? Also, how is the power adapter constructed? Is it built into the computer, or is it a separate unit?

What I'm getting at is this: Is it the power adapter being plugged in that's causing the hum, or is it the power adapter being plugged in and connected to the computer that's causing it? If you can, try plugging the adapter into the wall but leaving it disconnected from the computer and see if the hum occurs. This may help determine whether the adapter is causing general electrical interference or whether it's an issue with the power feed that the adapter is supplying.

It goes away when I unplug it from the computer. It's still plugged into the wall.

Also, I make sure to unplug everything else in the room when I'm recording to try and minimize interference, so the only thing that's ever plugged in is the computer.

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