# Laptop sound noise



## Corbettlight (Aug 6, 2009)

Hello,
When I have my laptop hooked into our sound board for music, effects, etc., it sounds great... Except when my laptop is charging. Is there any way I can fix this?

Thanks


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## DaveySimps (Aug 6, 2009)

Assuming you have no building power issues or poor cabling causing the hum, try one of these. I picked one up a couple of years ago, and it works great.

PAC SNI-1/3.5 Hum Killer Noise Filter Laptop Ipod MP3 - eBay (item 200366145511 end time Aug-22-09 10:53:38 PDT)

A more expensive but professional solution is the Whirlwind PC DI.
Whirlwind / Direct Boxes

Do swap out / check out your cabling and connections (both power and audio cables) to make sure there is nothing going on there causing it. 

~Dave


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## rwhealey (Aug 6, 2009)

I have heard that some laptops are particularly bad when plugged into a wall, even with a DI.

I have no personal experience with the situation, but could you get a different model of power supply for your laptop? That might solve the problem.


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## jkowtko (Aug 6, 2009)

Or get a "real" audio interface such as the M-Audio FastTrack Pro ... you'll enjoy the improved sound quality as well as getting rid of the hum


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## Corbettlight (Aug 6, 2009)

I actually have an M-Audio (Pro?) Duo for home recording. Is there a way I could incorporate that into my design?

Thanks


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## jkowtko (Aug 7, 2009)

From the manual:
http://www.m-audio.com/images/global/manuals/Duo-USB_Manual.pdf

It looks like it has balanced outputs, and "... With the “Standalone” switch in the Out position, the Line Outs receive audio from the computer’s software outputs... "

Then it should show up as an audio card for your playback programs. Looks like you might be in business ...


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## Corbettlight (Aug 7, 2009)

I don't have much experience with this stuff, how would go about hooking it into the system?


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## JohnHartman (Aug 7, 2009)

What laptop are you using? I know some Dell D630's have some issues with their soundcards and hum when plugged in.


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## Corbettlight (Aug 7, 2009)

I have an HP dv2700t.


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## jkowtko (Aug 13, 2009)

Corbettlight said:


> I don't have much experience with this stuff, how would go about hooking it into the system?



Just hook it up to the computer via the USB ports using a regular printer-style usb cable. Hopefully your Pro came with a USB cable. If not, grab a printer cable. Then connect your outputs to your sound mixer using TRS cables (1/4" stereo jacks) to get balanced signal through. They must be TRS cables, not TS cables. The TRS jack looks like a stereo headphone jack, the TS looks like a mono jack. 

Look at pages 4 and 5 in the manual:
P4, item 6: leave standalone switch in the OUT position
P5, item 2: connect via USB to your laptop
P5, item 4: use TRS cables to connect to input channels on your mixing board.
P5, item 5: leave Line Level switch in OUT position for +4dBu

You will also need to install the M-Audio software on your laptop. Once you do, a Control Panel should become available that let's you configure the M-Audio (which you shouldn't have to adjust from factory settings), but more importantly, the M-Audio will now show up as an output device option from your Windows programs.

Let us know how it goes.


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## ruinexplorer (Aug 13, 2009)

The solution jkowtko proposes is probably your best option. If you can't get that to work, the best options that I came up with are the use of an external sound card (connected via USB) or a sound filter like what has been mentioned or this one by D'san which is specifically for this purpose. I find that the laptops that have a grounded power supply are usually the biggest culprit of this type of noise.


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## gordonmcleod (Aug 14, 2009)

I have had goodluck with the USB pre 
USBPre Microphone Interface for Computer Audio | Sound Devices, LLC


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## g15 (Aug 14, 2009)

Have you tried a ground-lift?


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## museav (Aug 15, 2009)

g15 said:


> Have you tried a ground-lift?


Can you clarify what you mean?


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## g15 (Aug 17, 2009)

one of these
Ground Lift Adapter. Cooper 419GY

We have a dell laptop that makes the most horrible noises if it's plugged in and grounded. We ended up pulling the ground prong out and now it works great.


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## Chris15 (Aug 19, 2009)

g15 said:


> one of these
> Ground Lift Adapter. Cooper 419GY
> 
> We have a dell laptop that makes the most horrible noises if it's plugged in and grounded. We ended up pulling the ground prong out and now it works great.



DO NOT EVER USE THESE.

You defeat the purpose of the Earthing system. As I understand your convoluted electrical system, the purpose of these is that the lug gets bolted to the GPO case to provide the ground connection. Lift the ground and YOU could become the path to Earth under fault conditions...


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## jkowtko (Aug 19, 2009)

Not that I'm advocating using ground lifts, but doesn't the risk with AC adapters stop at the transformer (there's only a two-conductor, low voltage cord to the laptop itself) So, theoretically, if you keep the transformer wrapped up and close to the power outlet then your risk of electric shock is very localized.

This is of course different from rack mounted gear with three-conductor power cords running from the rack ...


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## Chris15 (Aug 19, 2009)

jkowtko said:


> Not that I'm advocating using ground lifts, but doesn't the risk with AC adapters stop at the transformer (there's only a two-conductor, low voltage cord to the laptop itself) So, theoretically, if you keep the transformer wrapped up and close to the power outlet then your risk of electric shock is very localized.
> 
> This is of course different from rack mounted gear with three-conductor power cords running from the rack ...



My laptop has a 3 pin clover leaf connector on the power supply. Just having got the meter out, the DC connector has it's outer grounded. It's a Dell and actually using a tricentric connectors with centre pin and then inside and outside of the shell.

Basically if it has a ground connection on the device, I would assume that grounding is necessary for the safe and optimal functioning of the device...


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## museav (Aug 19, 2009)

g15 said:


> one of these
> Ground Lift Adapter. Cooper 419GY
> 
> We have a dell laptop that makes the most horrible noises if it's plugged in and grounded. We ended up pulling the ground prong out and now it works great.


Please read the description in the link you referenced, you apparently are not using that adapter for the intended purpose. Adapters like those are intended to adapt modern three prong equipment that relies on a dedicated safety ground to older two conductor electrical system that used the boxes and conduit for the safety ground path. The metal tab connects to the center screw on the plate which via the metal face plate, box and conduit provides the safety ground path. Basically, those adapters are meant to provide a continuous safety ground path when using newer devices with older electrical distribution systems and not to break the ground path. Using them to do so is not only improper use of the device but also a code violation and dangerous.


jkowtko said:


> Not that I'm advocating using ground lifts, but doesn't the risk with AC adapters stop at the transformer (there's only a two-conductor, low voltage cord to the laptop itself) So, theoretically, if you keep the transformer wrapped up and close to the power outlet then your risk of electric shock is very localized.


In normal use, but not in the event of a failure, which is where the safety ground path may be critical. Imagine if the transformer failed in some way, without a safety ground where does that current go?

Devices with two prong plugs are usually Class 2 or 'double insulated' rated. [FONT=Verdana, Arial, Helvetica, sans-serif]This means that the devices are designed specifically to not require a safety ground and are instead[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif] required to prevent exposure to dangerous voltage or current from any failure without the use of a grounded metal casing. [/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]There are also strict requirements on the insulation resistance and leakage to any ground or signal connections. Double insulated devices do not, and should not, have a separate safety ground connection. However, any devices with a three prong plug or safety ground terminal should be assumed to potentially fail in a manner that could represent a shock hazard and thus they require a safety ground connection.[/FONT]


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## JohnHartman (Aug 20, 2009)

Make sure you are using the correct Dell power supply. There are 2 prong on the AC side and 3 prong on the AC side Dell power supplies and they are different though both will power the laptop. If you mix them, specifically using the 3 prong on a laptop that is expecting the be used with a 2 prong you will get hum and nasty noise on the laptop. It sounds like you may not have the right power supply, or a further power issue with your set-up.


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## bri4827 (Aug 20, 2009)

Corbettlight said:


> Hello,
> When I have my laptop hooked into our sound board for music, effects, etc., it sounds great... Except when my laptop is charging. Is there any way I can fix this?
> 
> Thanks



On any of my Dell laptops I have to use a ground lift while charging and playing back through a mixer. See if that helps


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## museav (Aug 20, 2009)

bri4827 said:


> On any of my Dell laptops I have to use a ground lift while charging and playing back through a mixer. See if that helps


Since you mentioned charging I assume you mean lifting the safety ground and not the audio signal ground. Did you read any of the previous posts in this thread? You know, the ones discussing how this was a code violation and potentially dangerous.

I use my Dell laptop, and have seen many others using Dell laptops, for system alignment and tuning where noise would be a real problem. We simply use a good quality external audio interface and after looking at the response of some internal sound cards, that is the way I would typically approach anything other than a temporary setup, in which case I might use a DI or input transformers. A safety ground lift may help assess a problem but it is not a solution in any situation.


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## g15 (Aug 21, 2009)

so then the proper thing to do is purchase one of these? Dell : Dell 2-Prong/2-Wire Flat US Power Cord for Select Dell Systems ? 3 ft : Computer Power Supply, Laptop Batteries & Surge Protectors : Small & Medium Business


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## museav (Aug 22, 2009)

g15 said:


> so then the proper thing to do is purchase one of these? Dell : Dell 2-Prong/2-Wire Flat US Power Cord for Select Dell Systems ? 3 ft : Computer Power Supply, Laptop Batteries & Surge Protectors : Small & Medium Business


Is it compatible with your power supply? That cord goes to the power supply and my Dell power supply uses a 3 prong plug, if that cord works with your power supply then you probably already have a two prong cord.


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## gdonhardt (Aug 24, 2009)

The problem is due to the switch mode power supply. Most modern laptops now have switched mode power supplies. These are generally the sole cause of audio system hum when using laptops. When you remove the switch mode power supply from your laptop the hum should be gone. There are a couple of alternatives to this. See if you can source a regular (non switch-mode) power supply for your laptop. This is probably the least favourable solution. The other solutions are to use an audio isolating transformer. This may remove some or all of the hum. But by far the best solution is to use a DI box, or other audio interface via firewire or usb.


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## Corbettlight (Aug 27, 2009)

Ok, I will try using my M-Audio interface. I do not, however, understand why this would eliminate the hum. Could someone enlighten me?

Oh, and it's not exactly a hum. It's more of an oscillating, periodic buzz. It sounds kind of muted, also. Like the upper harmonics are missing.


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## Chris15 (Aug 28, 2009)

Corbettlight said:


> Ok, I will try using my M-Audio interface. I do not, however, understand why this would eliminate the hum. Could someone enlighten me?
> 
> Oh, and it's not exactly a hum. It's more of an oscillating, periodic buzz. It sounds kind of muted, also. Like the upper harmonics are missing.



2 main reasons;
1- it gets the analog audio away from the EMI wandering around the motherboard on the laptop, and from the hard drive etc.
2- external interfaces are less worried about an extra 3 bucks in component cost and so generally have far better designed products...


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## Corbettlight (Aug 28, 2009)

Ok - so it's basically the sound being corrupted in the sound card of the laptop, not before it gets there?

I was just wondering why the external interface would help because the audio (signal, at least) will still be originating in the laptop, just travelling through a USB cable before being output through a TRS plug.


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## 00AVD (Aug 28, 2009)

With an external (USB) sound interface, the USB is carrying the audio as digital, not analogue. The (unwanted) noise is often introduced in the analogue stage, and since an external interface is often better designed, it doesn't suffer from the same problem.


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## Corbettlight (Aug 28, 2009)

OK cool.

Thanks guys!


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## db91977 (Mar 30, 2012)

Hi guys, 

My first post here. I found this thread while searching the Net for possible solutions to laptop computer power supply noise problems. I decided to join up, partly because I am a musician and recording/sound tech professionally, and partly so that I could tell you my experiences on this problem (and what I found to be the solution). 

I had been going 'round and 'round with this laptop noise problem for a few years- ever since I purchased a Sager (Clevo) M570-TU laptop for audio work in Aug. 2009. I typically use my M-Audio ProFire 2626 audio interface for recording work, along with various other audio gear- Mackie 1402-VLZ3 mixer, PreSonus HP4 headphone amp, etc.. When using the system with my Sager laptop, I kept getting an intermittent noise in my audio, consisting of a low-level, but very annoying, hashy, dirty hum (not primarily 60 Hz, but higher), mouse zipper noise, and other noises related to computer activity. For example, the frequency of the noise changed when I used a different audio buffer setting on the 2626. I tried a couple Radio Shack "Ground Loop Isolator" stereo cable assemblies between the ProFire 2626 and my mixer, which sometimes lessened the noise. But I would still get the noise in other equipment in the room, such as a bass guitar amp.

I found that if I disconnected the laptop power supply and ran the computer on its internal battery, the noise went away completely. This pretty much narrowed the problem down to the power brick, but I was at a loss about how to eliminate this problem, short of getting an expensive linear power supply for the laptop- I know that 13.8 VDC power supplies are common, but an 18 VDC supply capable of 6 Amps of current is probably harder to find, and more expensive. I lived with the problem for way too long. When I heard some of this noise getting onto a vocal track I was recording for a client, I said, ENOUGH.

At first, I assumed that the power supply was generating this noise. But it seems more likely to me that the power supply is acting as a path for noise generated in the laptop to travel back up through the DC cable, the power brick, and onto the AC power circuit via the ground pin. I don't have the test equipment to prove this, but that's my impression. If it was just the power brick generating the noise, why would this noise be affected by activity on the computer? And, when I disconnect the DC cable from the laptop, the noise goes away, even though the power brick is still plugged into the AC outlet. What's interesting to me also, is that the laptop noise is apparently NOT transmitted through the firewire cable to my audio interface- in that case, I would hear the noise in my audio even when running the laptop on the battery, no?

*The solution? Lift the ground pin of the laptop's power supply with a 50-cent 3-wire to 2-wire AC adapter, like the one G15 pointed to above. * I have not experienced any of the annoying "power supply" noise since. 

Now, I can understand the safety concerns about lifting the ground on an AC adapter, but practically speaking, we're not talking about a hazard of high-voltage AC on the laptop side here. We're not using a power tool with a metal casing. Any failure of the power brick on the AC side would be confined to the power supply, right? And besides, as some of you have observed above, many laptop power bricks come with 2-prong AC plugs. What, safety is a concern for some laptop power supplies and not others? I think the hazard is minimal at best. And, AT LAST, I have NO noise related to the laptop's power supply, in my audio system. I have gone over to the dark side, the ground-lifted side, the QUIET side.


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## museav (Mar 30, 2012)

db91977 said:


> *The solution? Lift the ground pin of the laptop's power supply with a 50-cent 3-wire to 2-wire AC adapter, like the one G15 pointed to above. * I have not experienced any of the annoying "power supply" noise since.
> 
> Now, I can understand the safety concerns about lifting the ground on an AC adapter, but practically speaking, we're not talking about a hazard of high-voltage AC on the laptop side here. We're not using a power tool with a metal casing. Any failure of the power brick on the AC side would be confined to the power supply, right? And besides, as some of you have observed above, many laptop power bricks come with 2-prong AC plugs. What, safety is a concern for some laptop power supplies and not others? I think the hazard is minimal at best. And, AT LAST, I have NO noise related to the laptop's power supply, in my audio system. I have gone over to the dark side, the ground-lifted side, the QUIET side.


Apparently you did not read the entire thread or the manual for your laptop that states "The power adapter may have either a 2-prong or a 3-prong grounded plug. The third prong is an important safety feature; do not defeat its purpose."

You appear to have some common misunderstandings. For one, there are no three wire to two wire adapters as those would create a code violation and an unsafe condition. What you are using is almost certainly an adapter intended to adapt the safety ground on a modern three wire plug to an older two prong electrical system that used a method other than a dedicated ground wire to the receptacle in order to provide the ground path, usually through a metal plate and/or box along with either a dedicated ground wire or metallic conduit from the box. The tab or wire on the adapter is intended to be used to create a continuous safety ground path from the third prong on the power supply to that alternative ground path, exactly the opposite of the ground connection being left disconnected or broken off in order to break the ground path.

For another, devices with two prong plugs are almost always double insulated and UL listed as such, meaning that they are designed so that an internal short cannot potentially make the external chassis 'hot' and tested to verify the effectiveness of the design. However, devices with a three prong plug instead rely on the ground to drain off the voltage and current in case the chassis or device body somehow becomes 'hot'. Don't think that the power supply having plastic body prevents the outside of the supply or the cable to the laptop from potentially becoming 'hot'. Break the safety ground path of your power supply and if the chassis ever does become 'hot' then any other potential ground path including a person touching the power supply could be subject to the full voltage and current of the circuit (which is also what leads to the one exception to the potential problem if using a GFCI circuit).

This is one of those situations where the likelihood of breaking the safety ground path actually becoming a problem is very small, however the potential outcome if that happened could be extreme. So you haven't really gone to the dark side, more to the potentially dark and crispy toasted side.

Instead or risking your or someone else's life, get some good audio isolation transformers, use a FireWire or USB interface or find a replacement two prong, double insulated power supply.


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## FMEng (Mar 30, 2012)

Brad is correct. Lifting the AC ground in the manner described is not safe. Ebtech makes a product that opens the ground for low potentials but completes the circuit for hazardous potentials. Yes, it costs a few dollars, but it could prevent a death.

Ebtech - Audio Solutions

Often there are better approaches to stopping hum and noise problems, like dropping shields on balanced lines, and/or using good quality audio transformers with Faraday shields. In this case, the Ebtech might be a nice solution.


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## museav (Mar 31, 2012)

FMEng said:


> Brad is correct. Lifting the AC ground in the manner described is not safe. Ebtech makes a product that opens the ground for low potentials but completes the circuit for hazardous potentials. Yes, it costs a few dollars, but it could prevent a death.
> 
> Ebtech - Audio Solutions
> 
> Often there are better approaches to stopping hum and noise problems, like dropping shields on balanced lines, and/or using good quality audio transformers with Faraday shields. In this case, the Ebtech might be a nice solution.


The HumX is definitely a step up from completely breaking the ground path but I personally avoid them. Apparently the HumX uses a pair of parallel diodes, one in each direction, which effectively breaks the safety ground path until the diodes see sufficient voltage to start passing current. However, the HumX is only rated for 6A, the current capacity could be increased but the device would probably need to be physically larger and more expensive. This not only means the current capacity of the HumX is less than that of the receptacle or circuit into which it would be plugged, but it also results in having a 6A rated device with a 15A rated receptacle and plug and no fuse or other overcurrent protection, which may be one reason why the HumX is not UL listed. But my biggest concern is that I have had multiple people who know much more about the details than I do and whose expertise on the topic I highly respect state that full circuit current or a surge could cause the 6A diodes to burn out, leaving you with no ground path right when you most need it.

For the price of an Ebtech HumX you might be able to find a compatible double insulated power supply which should address any ground loop issues and also allow your current power supply to serve as a backup or spare.


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## FMEng (Mar 31, 2012)

The long term current rating of the diode does not tell the story. Without lab testing, we don't know if the Hum-X can handle the total short of a 20 Amp branch circuit long enough to trip a circuit breaker. I'd bet that it would do that, but it probably sacrifices itself in the process, which is why they put the indicator light on it. If they didn't design it that way, the lawsuits would be the end the company. We also don't know if there is a one-time fuse built into it to limit it to the 6 amp rating. The "fuse" could be as simple as a printed trace of specific dimensions.

Having said that, using the Hum-X would not be my first choice in solving a noise problem. The design is a bit shady as you point out.

As for UL ratings, they aren't worth much. I once encountered a bunch of new computer monitors that had 90V of leakage to the VGA cable shield. They had a UL listing, so I called UL to report it and they could not care less. All they want is the money to test one example of the product. If the production release of it kills someone, they have no liability.


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## db91977 (Apr 2, 2012)

So much for everybody welcoming me to the forum on my first posting here.  I post a lengthy message detailing my observations and experiences, and I get ripped a new one for something I said in it. Thanks! And btw Brad, I did read every post in the thread prior to my post. 

Granted that lifting the ground on an AC plug is not the recommended solution. But it does work in my case, and the risks I take in doing so are my own. Living life is a calculated risk. And some people have a higher risk tolerance than others. In my opinion, the risk in this case is vanishingly low- lower than the possibility of getting struck by lightning while walking to the store, or being T-boned by a drunk pickup truck driver at an intersection. We should take a survey- how many cases has anybody seen of laptop power supplies failing catastrophically and resulting in injury or death to a nearby person? 

As FMEng points out, a UL rating on a product does not automatically make it safe under all conditions. There are caveats in using any product, following the usage and safety recommendations or not, and if you like to juggle running chain saws, and have that ability, more power to you. 

Now, can anybody address any of the other points in my post, such as thoughts about the possibility of filtering AC components out of the DC side of switching power supplies, so that we can stop the noise nearest to the source, and not have to apply "band-aid" solutions to our audio equipment? 

--db


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## 65535 (Apr 2, 2012)

Laptop power supplies are notorious for creating a lot of noise. The sound card or integrated sound commonly picks up that noise and puts it through to the output. There it is amplified by the gain stage of the sound console and amplifiers.

Chances are lifting the ground won't make a bit of difference because the noise is part of the signal and not a ground bias issue. You're best bet is using an external audio interface over Firewire or USB, a good unit will filter the bus power and eliminate the noise. They also are capable of multi channel out and proper +4dBu levels.

The reason you don't get noise on battery power is because it's a stable DC source.


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## gafftaper (Apr 3, 2012)

I want to put in an official CB safety statement here. Regardless of what some people in this thread believe, it is never a good idea to remove proper grounding. When you remove grounding, regardless of which piece of equipment you are talking about, you open yourself up to a new world of potential danger to both your equipment and yourself. Electricity can and does kill people. Removing the ground is the electrical equivalent of rigging with Chinese made shackles or hanging lighting instruments without a safety cable. Yeah you might be okay for a while, but you are flirting with serious danger. Don't do it.


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## SHARYNF (Apr 3, 2012)

gafftaper said:


> I want to put in an official CB safety statement here. Regardless of what some people in this thread believe, it is never a good idea to remove proper grounding. When you remove grounding, regardless of which piece of equipment you are talking about, you open yourself up to a new world of potential danger to both your equipment and yourself. Electricity can and does kill people. Removing the ground is the electrical equivalent of rigging with Chinese made shackles or hanging lighting instruments without a safety cable. Yeah you might be okay for a while, but you are flirting with serious danger. Don't do it.



Let me just add to the controversy:

The basic issue is that the notebook power supply combination that exhibits this noise issue is incorrectly designed/implemented. I have had this issue with some Dell units, and finally got dell to give me another power supply. I have not found this on any of the more recent models.

SO here is the problem as I see it:
If you lift the ac ground, and the notebook/power supply has a problem, you have a dangerous situation
BUT if you leave the ground connected and elsewhere in the ac system you are connected to has a problem, then you have a dangerous situation as well since you basically have a connection between ground and the power system in a improperly insulated device. (two prong devices are supposed to be doubly insulated) This is why for instance a lot of hand power tools only have a two prong ac connector. 
Sharyn


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## ruinexplorer (Apr 4, 2012)

db91977 said:


> So much for everybody welcoming me to the forum on my first posting here.  I post a lengthy message detailing my observations and experiences, and I get ripped a new one for something I said in it. Thanks! And btw Brad, I did read every post in the thread prior to my post.



Sorry you did not feel too welcomed, but safety is a primary concern here on this forum. We have to make sure that point is hammered in no matter how long members are on the forum.


> Granted that lifting the ground on an AC plug is not the recommended solution. But it does work in my case, and the risks I take in doing so are my own. Living life is a calculated risk. And some people have a higher risk tolerance than others. In my opinion, the risk in this case is vanishingly low- lower than the possibility of getting struck by lightning while walking to the store, or being T-boned by a drunk pickup truck driver at an intersection. We should take a survey- how many cases has anybody seen of laptop power supplies failing catastrophically and resulting in injury or death to a nearby person?



When you share essentially recommend defeating a safety feature, you remove that calculated risk to yourself and spread it to others: "The solution? Lift the ground pin of the laptop's power supply with a 50-cent 3-wire to 2-wire AC adapter, like the one G15 pointed to above." You even bolded this text. This emphasis makes it sound as if you do not care about the safety of others. How many have died from it? I guess we could research this for you. However, the general consumer or IT manager is not likely to defeat this safety feature. I have only known people in the entertainment industry to do so. 


> As FMEng points out, a UL rating on a product does not automatically make it safe under all conditions. There are caveats in using any product, following the usage and safety recommendations or not, and if you like to juggle running chain saws, and have that ability, more power to you.



No, but the UL listing is going to help you for insurance purposes, defeating it will not. Also, if there is a workplace industry caused by knowingly defeating a safety device, you risk heavy fines from OSHA. 


> Now, can anybody address any of the other points in my post, such as thoughts about the possibility of filtering AC components out of the DC side of switching power supplies, so that we can stop the noise nearest to the source, and not have to apply "band-aid" solutions to our audio equipment?
> 
> --db



This is the real issue. Since this is not the intended purpose of laptops, this is not the main concern of the engineers. Should we become a main source of income for the laptop industry (never going to happen), then I am positive that the manufacturers would spend their efforts on solving this problem. In the mean time, we should only use safe alternatives. Several alternatives have been suggested, and I would suggest that the replacement of your power supply would likely be the best option for you.


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## BGW (Apr 4, 2012)

Wouldn't an isolation transformer eliminate those ground loops?


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## SHARYNF (Apr 4, 2012)

Actually your point re this not being the intended purpose of laptops is misleading IMO
What we are seeing here is a design flaw, that again in my experience COULD lead to a dangerous situation of the same level as removing the ground pin. IF there were another fault on a device on the same AC connection the problem outlined shows that it would be possible for this fault to be connected directly to the laptop.

What people are missing is that the noise issue shows that there is an improper connection between the AC ground and the "ground" negative side of the audio circuit.

Sharyn


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## BGW (Apr 4, 2012)

SHARYNF said:


> What people are missing is that the noise issue shows that there is an improper connection between the AC ground and the "ground" negative side of the audio circuit.
> 
> Sharyn



I agree that the laptop PS are faulty in that way, but I disagree with the above. Tons of pro equipment, the majority, tie the signal ground and the chassis ground together. Most of the good equipment also features a "ground lift" switch or jumper, which floats the _signal ground _from the chassis_._ *Those switches/jumpers may be misleading as some people think they float the chassis ground (safety ground/earth) which they most certainly do not.*


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## museav (Apr 4, 2012)

BGW said:


> I agree that the laptop PS are faulty in that way, but I disagree with the above. Tons of pro equipment, the majority, tie the signal ground and the chassis ground together. Most of the good equipment also features a "ground lift" switch or jumper, which floats the _signal ground _from the chassis_._ *Those switches/jumpers may be misleading as some people think they float the chassis ground (safety ground/earth) which they most certainly do not.*


As you noted, many audio devices have the shields (Pin 1 on an XLR) tied to the audio reference ground when they should be tied to the chassis which is in turn tied to the electrical system ground such that any current on the audio cable shield runs direct to ground and not via the device's audio circuitry reference ground. I think that may be what Sharyn was referencing. Good equipment should be in accordance with AES48 and thus not require a ground lift switch, dropping a conductor at either end or any of the other common 'fixes' in order to avoid ground loops.


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## SHARYNF (Apr 5, 2012)

Yes that is the problem:

Here we have a combination of factors, one is that the headphone output jack on a notebook is not a shielded balanced system, and the power distribution in the notebook has to deal with two sources of power, both battery and external. It is not like the external power simply charges the battery, since in a lot of notebooks you can remove the battery and still run the laptop on the external power supply.

What I have found and others have suggested is simply get your self a external USB or firewire audio system, so that you simply do NOT use the headphone jack, and bypass the entire audio ground issues



Sharyn


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## db91977 (Apr 13, 2012)

I did look around for a replacement power supply for my laptop which has no ground pin on the AC plug, but I couldn't find one. I'll continue to look around- maybe someone knows of a laptop power brick supplying 18-24V DC at 6A, with a two-prong AC plug. 

I did come up with a temporary solution to the noise problem which seems to work well, however. I have two 8-channel mic preamps: an M-Audio Profire 2626, and a Behringer ADA8000. My laptop is hooked up via firewire to the 2626. In my audio software, I send my outputs from the 2626, via ADAT optical, to the ADA8000. This unit's D/A converter outputs the audio onto its 8 XLR connectors, which I connect to my mixer. The result: super-clean audio, no hum, buzz, or digital noise at all. I think this works because the AC adapter for the Profire 2626 is two-prong. The ground is broken at that point. And, since I'm sending the audio out via ADAT, there is no signal ground either.


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## db91977 (Apr 13, 2012)

SHARYNF said:


> What I have found and others have suggested is simply get your self a external USB or firewire audio system, so that you simply do NOT use the headphone jack, and bypass the entire audio ground issues
> 
> Sharyn



I would like to point out, Sharyn, that many of us ARE using external audio interfaces (myself included) and still get these laptop power supply noises in the audio interface. In my case, I believe that the shield of the firewire cable is carrying these noises into the Profire 2626 audio interface. But if I send the audio from the 2626 out thru ADAT, the noise is not carried with it. Just food for thought, and a possible solution, for those of you who have the extra equipment. 

--db


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## Chris15 (Apr 13, 2012)

Amazing what some galvanic isolation can do...
ADAT being an optical signal can NEVER cause ground loops - but they may sneak in through other copper gremlins.

I think the key to remember here is that it is ultimately the device that does the digital - analog conversion that governs the noise, buzz and other pain in the system.
If it has issues, the system will have issues...


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## howlingwolf487 (Apr 14, 2012)

In this situation, the ADAT optical interface is very similar to an opto-splitter/isolator used for DMX distribution, etc. There is no physical connection, so those problems are a nonissue and moot.


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## rvhalejr (Jul 10, 2012)

howlingwolf487 said:


> In this situation, the ADAT optical interface is very similar to an opto-splitter/isolator used for DMX distribution, etc. There is no physical connection, so those problems are a nonissue and moot.



Good things opto-isolators, isolation transformers and 1:1 isolation amplifiers.

I do not have much to say other than I've been annoyed enough to ask a relatively well regarded manufacturer of sound gear to send me some schematics in hopes of finding a solution to this problem.

So after reading this thread, looking at schematics and specifications I was wondering what some of the rocket scientists I was fortunate enough to work with in another life would do. Well, they would likely have pointed out that instrumentation op amps across the post power source mains feeding a sensitive differentiation amp could trip ye old crow bar as us old timers used to call electronic circuit breakers.

Well, looks like some clever countries are using such devices called RCDs "A two-pole residual current device" and the wiki page has a nice picture that looks just like the one on ebay for about $10 and probably another $10 for shipping. There is some good science behind the device (crowbars before arrhythmia can kick in) but like all things (GFIs) they can be defeated if we are clever or work hard enough at it or Murphy's Law kicks in.

(I wonder how it handles the voltage drop across the device from heat, amplification, etc., would seem to need a sample and store characteristic curves in the comparator).

My laptop uses 20V @ 5A max and working hot in a lab with 20V DC is, well, wimpy compared to 110v AC which can definitely be lethal. If I were to conduct a FMEA (safety analysis) the only thing in a recording studio to treat with **LOTS** of respect would be Tube devices which are all the rage now (leaving dinosaurs like me scratching our heads).

Theaters in general could be very dangerous w.r.t. Lighting if not given respect. Standard Operating Procedures generally should be followed and Multiply redundant Safety Systems implemented whenever possible (like the insulation on two prong devices mentioned here one would suppose).

Batteries are generally safe but even a 12v car battery will be very unforgiving across a dead short and since we earthlings have a lot of salinity (electrolyte - conducts electricity really, really well) prudent behavior is a very good idea. 

So for now I'm running the laptop on battery power and eventually may replace the old tower power supply with one from Antec (reported to be stone cold quiet w.r.t. EMI/RF). 

I tried out a tube pre-amp recently but the idea of running 400V to bias the valves (what they call tubes now) is not for me at this time (the heat it put off rang some alarm bells).

Oh, and those nice rugs on stages for performers using mic stands, not just for sound deadening but also provides another layer of insulation. Not a problem though with highly mobile RF mics.

I've also made the assumption that high shielded (properly terminated) cables are being used for microphones and instruments. 

So....
(1) If you can walk around with it two prongs are probably o.k. just be careful (Stun guns are two prongs, fit in a pocket, but what a wallop that arc carries).

(2) If you cannot carry it three prongs are needed (and lots of respect).


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## museav (Jul 10, 2012)

rvhalejr said:


> So....
> (1) If you can walk around with it two prongs are probably o.k. just be careful (Stun guns are two prongs, fit in a pocket, but what a wallop that arc carries).
> 
> (2) If you cannot carry it three prongs are needed (and lots of respect).


As we live in a country where someone sued the mower manufacturer for not telling them to not use the mower in such a manner after being injured while trying to use their lawnmower to trim hedges, regardless of whether you can carry a device or even if it carries itself around on its own, I think the only appropriate assumption is that if the power plug on the device has three prongs then the ground pin is there for a reason and that defeating it increases your risk.


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## headcrab (Jul 10, 2012)

In the last two laptop power supplies I hacked apart, the AC ground only connected to the DC ground and nowhere else. Not that there's anything else to ground in a switching power supply.

I still don't approve of defeating grounds.


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## JohnHartman (Jul 10, 2012)

I think part of this is the manufacturers do not pay huge attention to these types of issues, they get parts from various suppliers and pack them based on the cheapest price. I have 2 power supplies that came packed in 2 new Dell D630 laptops back then they were new. Here are the specs:
Family: PA-12
Input: 100-240V~1.5A 50/60Hz
Output: 19.5V DC 3.34A
Differences one is listed as Model FA65NS0-00
the other as Model AA22850

One if 2 prong, the other is 3 prong. One when used the audio makes noise, the other does not.
Its not a grounding noise, it is noise from the power supply. Dell's answer use a external USB audio board.

Go figure..


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## rvhalejr (Jul 10, 2012)

museav said:


> As we live in a country where someone sued the mower manufacturer for not telling them to not use the mower in such a manner after being injured while trying to use their lawnmower to trim hedges, regardless of whether you can carry a device or even if it carries itself around on its own, I think the only appropriate assumption is that if the power plug on the device has three prongs then the ground pin is there for a reason and that defeating it increases your risk.



Sounds Good to Me (No pun intended). But on the flip side Electrical Engineers and Electronic Device Designers see amps, laptops, lighting, power generators, mains, sub-stations, etc. as big white boxes and (being qualified to do so) tend to discriminate between signal ground and power ground. 

Obviously things that fly (airplanes and satellites) are out of scope here but they do tend to work without a real earth ground. Aerospace circuitry (Moog comes to mind) can find its way into the theater. But what Engineers and Scientists do in the lab is not what we are talking about.

Hence, I'm including a few references that have taught me a number of things and recommend them as required reading for anyone (including Scientists and Engineers) in the Industry:


References
**************
BBC WORKPLACE - 'EGN3 Electrical Guidance Note 3';
5 Special case - Performing Band electrical and musical equipment
bbc.co.uk/safety/pdf/safety-egn_3_rcds_v2-2_f.pdf 

Electrical Guidance Note 4 : Mains isolating transformers (ENG4) Covers Three Phase and other Extreme Industrial Hazards.
bbc.co.uk/safety/pdf/safety-egn-4.pdf

"Electrical safety at places of entertainment" Health and Safety Executive
bigtopmania.co.uk/pdf_downloads/electrical_guidance_documents/Hse_electrical_safety_at_places_of_entertainment.pdf

WORKSAFE WESTERN AUSTRALIA COMMISSION -- 
ELECTRICITY: RESIDUAL CURRENT DEVICES
OSHA Guidance -- Protection against earth leakage current when portable equipment in use
rigsafegear.com/docs/resource/Worksafe Codes/Electricity.pdf

THE Magazine For Mobile DJs -- Residual Current Devices
PRO MOBILE, THE magazine for Mobile DJs
promobile.org.uk/viewarticle.php?id=78&PHPSESSID=94830daed79ea35a6a081ce88e46a0bb

DISCLAIMER
*********
Obviously not a complete list, please append as you fit. 

As a Safety Officer I'd admonish electricians from working "Hot" and require a true earth ground (in the case of facilities that is a ground penetrating 10-15 foot copper pole with 2" ground straps running to every lab, stage, studio, etc.)...


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## rvhalejr (Jul 10, 2012)

!!! HAZARD !!! DVOM measurement Dell Laptop 20V 5A switching supply ground pin to building earth ground 60VAC (USA 110AC more or less).


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## headcrab (Jul 10, 2012)

What kind of meter did you measure that with? A lot of switching power supplies have caps from the ungrounded and grounded conductors to the grounding conductor. A voltage can be measured but no significant current flows.


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## rvhalejr (Jul 10, 2012)

headcrab said:


> What kind of meter did you measure that with? A lot of switching power supplies have caps from the ungrounded and grounded conductors to the grounding conductor. A voltage can be measured but no significant current flows.




123.5v Across rails, 60V AC Across Switching Power Supply Pin to Wall Ground (No Load Infinite Resistance).

**** thing visibly Arc'd when I plugged it in. Having tested 20KV connectors for Corona I'm still respectful of even small arcs as the instantaneous voltage across air in that milli- (or micro- second in the high frequency domain) is exponentially higher than what is measured on a DVOM (upwards of a million ohms impedance on the input of a typical Digital Volt Ohm Meter). 

Where is that digital storage scope when you need one ?

I just witnessed at least a 1KV instantaneous spike across a (60v ?) Chinese or Mexican cap with a dielectric that will certainly fail (short) after a finite number of spikes (plugging it in with everything "On" a worse case test scenario - but a real one none the less).

For personnel reasons out of scope here I do not fear death. Full load is playing KLOVE (iTunes under Religion) right now just below distortion fed into a balanced three way cross-over. I need the laptop as a DAW and/or backing track or two.

Do not draw any "Safe" conclusions unless a lot of your professional life was spent in "Failure Analysis" of high potential effects.

Evertime a dielectric experiences a voltage spike a microscopic conductive well begins to be formed. Sure, no uamps until that well gets close enough to the rail. Then catastrophic failure, hopefully with no human near the thing. I have not checked recent theory but a nano "plasma" model probably fits.

Oh, when a 20KV Corona Test fails it sounds like a half stick of dynamite going off. At the same worksite (Power Plant OEM) an electrician died outside my window. F---ing working HOT.

Mother nature will and does readily kill those who do not respect her.


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## rvhalejr (Jul 11, 2012)

Anybody try this ???

"Universal notebook power adapter 
- Compatible with models from Dell, Toshiba, Acer, HP, Sony, Fujitsu, Compaq, ASUS & more. For a complete list, visit" antec.com/snp90

"And with seven detachable connectors, the SNP90 works with virtually any notebook on the market, including the latest models from Dell, Toshiba, Acer, HP, Sony and more. Lighten your load and charge your notebook with 90 watts of Continuous Power with one notebook power adapter: Antec's SNP90." $60
store.antec.com/Product/notebookadapter/snp90/0-761345-22090-3.aspx


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## rvhalejr (Jul 11, 2012)

$46 on Amazon, reviews favorable except for recent Dell Studio Series which is reportedly chipped to recognize and use OEM chargers only (HP reportedly does this as well). IMHO they have gone overboard with these models, targeted at video editing and multimedia in general. Sort of like tower wanna-bees masquerading as laptops (and Rolex watches to match no doubt).

Professional editing is probably a joke as laptop I/O on the internal buss(es) will never approach that of a well designed tower. But hey, what ever floats your boat.

Worth a try on older laptops unless audio is reportedly trashy which would be uncharacteristic of Antec.

The SNP90 seems to have all sorts of connectors (as opposed to the slightly cheaper NP90 with one connector ?).

I have no monetary or other interest in this (did I really need to say that ?)...


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## museav (Jul 11, 2012)

rvhalejr said:


> Sounds Good to Me (No pun intended). But on the flip side Electrical Engineers and Electronic Device Designers see amps, laptops, lighting, power generators, mains, sub-stations, etc. as big white boxes and (being qualified to do so) tend to discriminate between signal ground and power ground.


I prefer the terminology signal ground and safety ground, as that is really what they are. The reason we have to worry about ground loops is basically because many Electronic Device Designers have been lazy, cheap or simply ignorant and have not properly addressed the path of the signal ground to the safety ground. If that is properly addressed, for example per AES Standard » AES48-2005 (r2010): AES standard on interconnections - Grounding and EMC practices - Shields of connectors in audio equipment containing active circuitry, then ground loops would not be such a common issue for audio devices.


rvhalejr said:


> As a Safety Officer I'd admonish electricians from working "Hot" and require a true earth ground (in the case of facilities that is a ground penetrating 10-15 foot copper pole with 2" ground straps running to every lab, stage, studio, etc.)...


I believe that the important point is having a reliable, very low impedance path to that single earth ground point for the building. Some facilities may use a single ground electrode rod while others use mulitple bonded rods within a small area. And some critical facilities or those with certain soil conditions may utilize a chemical/electrolytic ground electrode rather than copper rod(s).


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## DrPinto (Jul 11, 2012)

museav said:


> I prefer the terminology signal ground and safety ground, as that is really what they are.



I like that a lot. I'm going to start using those terms too.


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## headcrab (Jul 11, 2012)

I think there's too much emphasis on having ground rods. Sure, they (or some equivalent) are required by code, and they may have value, but wouldn't it be better to ensure a proper grounding system that originates at the neutral-ground bond at the upstream transformer?

And how do you get a very low impedance with a ground rod when the earth isn't made of copper?


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## rvhalejr (Jul 11, 2012)

museav said:


> And some critical facilities or those with certain soil conditions may utilize a chemical/electrolytic ground electrode rather than copper rod(s).



Yep. I don't see the copper rod working unless the surrounding soil has been treated electrolyticly and even then some locations and soil types make actual earth grounding impossible[1]. As far as I know there is no guarantee that there won't be a voltage differential between power utility ground and earth ground, I'm way out of bounds here as the only place we had that done (copper rod to some code) was manufacturing medical linear accelerators.

In control booth context there is, however, a probability that some venues will have a ground that likes to float regardless of how much engineering is thrown at it. I'd guess most facility engineers would know their site pretty well, the most likely problematic ones might be new where the contractor never bothered to check utility ground to earth ground (and or ignored the fact that a lot of construction workers were experiencing more shocks than normal). Codes vary from one locale to another so there are places where not much can be done (and not everyone will follow code anyway).

But I'm off on a tangent here (It's a writer thing?). 

I'd like to that everyone for their comments and hope hijacking this thread did not step on to many toes. I'm very pleased to find that Antec provides a noise solution for towers and laptops (I did not find that out until last evening).

Unless we see posts to the contrary I'll assume Antec power supply upgrades are the preferred solution and will pass that information on.

Best Regards,

Richard V. Hale Jr.

[1] Its been a while but I think some power plant control rooms use really big isolation transformers which might provide an artificial ground in an extremely hostile environment. Also power plants relatively close to one another may have to run in phase or they will trash earth ground and loose power in the process. More useless stuff I'm not sure of but can be researched if anyone is interested.


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## TimmyP1955 (Jul 22, 2012)

rvhalejr said:


> !!! HAZARD !!! DVOM measurement Dell Laptop 20V 5A switching supply ground pin to building earth ground 60VAC (USA 110AC more or less).



Whether it's a hazard depends on how much current it can deliver. Many things measure such an offset, but cannot deliver enough current to harm a mouse, let alone a human.


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## llecount (Aug 24, 2012)

So what IS the answer to this problem then? I've tried PC-DI's, iso transformers, different cables, etc and I still cannot get rid of this noise. I can make it quieter, but it is still audible, and that is not acceptable. This is on a sound system in a meeting room. Laptops with 2 prong wall plugs do not have any problem, but laptops with 3 prong wall plugs are noisy as hell. A USB/Firewire solution is not practical for a room such as this. 
Is there an affordable solution?


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## museav (Aug 24, 2012)

llecount said:


> A USB/Firewire solution is not practical for a room such as this.


Even something like Peavey :: USB-P USB Playback? It requires no drivers, although you do have to select it as your audio device.

Something like http://www.jensen-transformers.com/datashts/ci2mini.pdf should take care of ground loops, however the audio system in the meeting room probably can't tell unwanted noise from wanted signal so if the noise is inherent in the audio signal from the laptop then there is no easy way to address that other than perhaps trying to find an ungrounded power supply for the laptop or running off the battery.


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## rvhalejr (Aug 26, 2012)

In public forms we are constrained as to the message we convey. 

Looking at other meeting room setups might tell you the practice at your locale (facilities and electrical engineering probably let it the laptops float).

I know its not the safest practice but I plead guilty to doing the same thing as the carpeting and pad are thick in our meeting room (on the second floor) providing a good deal of insulation. If the room had no carpet (concrete ground floor) then I'd at least lay down some rugs before using power amps.

Spilling a drink on a three to two prong adapter on a concrete floor is not good. Even with carpeting on top of concrete is little help if the drink has electrolytes (conducts electricity) in it. Maybe not allowing drinks in the room might mitigate the situation. 

Sadly all the good solutions require investment. Upgrading to noiseless power supplies ($40 antec for all but a few newer laptops) would allow recharging of batteries during operation. They also could be swapped between machines that have just been charged with those running on a low battery.


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## Chris15 (Aug 26, 2012)

I don't want to be rude about it, but...

You can't go and expect good audio quality from an onboard sound interface that costs under a dollar to make.

If you want decent sound, there are no free lunches in this world and you'll need to pay for a proper audio interface.

ANY solution that involves compromising safety grounding included by a manufacturer means YOU are PERSONALLY LIABLE for any injuries caused.
Just don't do it.
No show is ever worth a risk to people's wellbeing. EVER.


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## FMEng (Aug 26, 2012)

There are two possible ways for the noise to occur. One is that the noise is produced in the sound circuitry of the laptop. It may simply be a case of power supply noise getting into the output. If that's the case, the only choices are to use an external sound device on the USB port, or use a different computer. The problem with a USB sound "card" is that the machine will have to have the proper drivers and settings.

The more likely possibility is that the noise is a ground loop and a good direct box or transfomer should do the job. The problem is that the quality of isolation of these products varies widely. Some use audio transformers with Faraday shields and some do not. Without the Faraday shield, there is capacitive coupling between the primary and secondary. Since the computer's switching supply makes a lot of high frequency dirt, it tends to pass through more easily than 60 Hz. 

It's hard to know which manufacturers are cutting corners. Generally, the more expensive the product, the better the result, as they should have better transformers. This is why there are $40 interfaces and $300 interfaces that seemingly do the same thing. The Jensen products are top notch and I have had great results with them. Countryman also has an excellent reputation. I would stay away from Rolls and Behringer. Also, make sure that the DI or transformer is feeding balanced cabling and a true balanced input on your mixer.


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## rvhalejr (Aug 28, 2012)

FMEng said:


> The problem with a USB sound "card" is that the machine will have to have the proper drivers and settings...
> 
> I would stay away from ... Behringer. .



*NO and NO.* I'm using the Behringer UCA202 from the laptop USB to the phono preamp input on an ancient stereo amp. The drivers are ROMed on the device (XP SP3). MS probably distributes it by default by now. There is absolutely no noise with this setup (admittedly far from perfect as it
is 16bit streaming audio. I have not run the 24bit tape/digital recording test).

I have no interest in Antec. The power supplies come with extremely high review recommendations. Call them up (or email) and ask them if you can return it if it is noisy. My understanding is that this would be a first ***AND*** everyone here would like to know about it.


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## FMEng (Aug 28, 2012)

I'm glad you have had good luck with the UCA202. I was thinking more of their direct boxes which haven't given me great performance and did not last long. In a meeting room situation, a USB device would require individual users to change their laptop sound settings. That is often beyond their capability. Plugging in an audio cable is about the all that can be expected.

You do realize that phono preamps apply RIAA equalization, which applies a 20 dB boost at 20 Hz., and a -20 dB roll-off at 20 kHz? The only thing a phono input is good for is connecting a turntable.


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## rvhalejr (Aug 29, 2012)

FMEng said:


> I'm glad you have had good luck with the UCA202....
> 
> .... You do realize that phono preamps apply RIAA equalization, which applies a 20 dB boost at 20 Hz., and a -20 dB roll-off at 20 kHz? The only thing a phono input is good for is connecting a turntable.



I had a nice long reply but the machine ate it with a 404. Did not see the little "restore saved content" box, oh well... a few highlights:

Assuming a DAW class:
Cntl pnl/sounds and audio/audio/sound playback/Default device/UCA202


I did not want to drag curves into the thread. Its nice to get your input though, thanks.

The digital to analog signal is pre-eq'd with -6db 20hz and +6db 20Khz slope in itunes with the pivot point (0db) at 500hz (dinosaur school).

Those old pre-amps are lots of fun, all the rage with musicians (and some broadcasters) but mine is transistor. Second stage EQ is through a hardware ten-band amped up to about 70 watts rms and fed into a five way cross over custom hand built speaker box network (half JBL studio monitors).

Hardware EQ set at the familiar gentile S curve everyone should recognize, know and love.

A phono input is formally defined as an instrumentation amplifier which to understand requires at least one engineering book (I have a few around here somewhere). All I care about I cranking it up to about 70watts rms, near deafining spl with no noise or distortion when compared to the headphone headset.

Whats not to like about the $40 Antec solution ? That it does not work with newer proprietary lap tops is not relevant. Antec makes Tower supplies so duh, log in remotely, use the Tower as a real DAW Server. The laptop (or notebook) is just a display device.

Cheers !!!


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## FMEng (Aug 29, 2012)

rvhalejr said:


> Whats not to like about the $40 Antec solution ? That it does not work with newer proprietary lap tops is not relevant. Antec makes Tower supplies so duh, log in remotely, use the Tower as a real DAW Server. The laptop (or notebook) is just a display device.
> 
> Cheers !!!



In the most recent scenario discussed here, it's a conference room or meeting hall, where we have no control over who is bringing in what computer. There may be no technical supervision. The solution has to be simple to untrained users and universal to any computer carried into the room. A solution that works fine in a controlled environment, like a theater control booth, studio, or home doesn't apply here.


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## rvhalejr (Aug 30, 2012)

FMEng said:


> In the most recent scenario discussed here, it's a conference room or meeting hall, where we have no control over who is bringing in what computer. There may be no technical supervision....



*YIKES!!!* Ushers at the bigger church venues (meeting halls) sometimes call this mob control. That would seem to only allow battery power.

Battery power is fine for the (executive) conference room and when batteries run low swap in another battery or if there are power outlets around the table plug in the $40 Antec and recharge without noise.

I'm looking for the problem here and cannot find one. Please educate me as I'm a life long student of the signal to noise ratio discipline. Thanks beforehand.


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## chausman (Aug 30, 2012)

rvhalejr said:


> I'm looking for the problem here and cannot find one. Please educate me as I'm a life long student of the signal to noise ratio discipline. Thanks beforehand.




rvhalejr said:


> Whats not to like about the $40 Antec solution ? *That it does not work with newer proprietary lap tops* is not relevant. Antec makes Tower supplies so duh, log in remotely, use the Tower as a real DAW Server. The laptop (or notebook) is just a display device.



That, is the problem. In one year at my high school, we've had everything from laptops running Windows 2000, to 2012 MacBook Airs, and everything in between. With people who just learned how to use PowerPoint for that event, to people who have years of experience. There is no way I could say (You just need to log in remotely, and connect to your computer, and then mine will actually supply the audio.


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## FMEng (Aug 31, 2012)

I guess my point is being missed here. There aren't too many situations where we can dictate to run on battery only, use only a certain brand of power supply, use a different computer, stand on your head and cough, to eliminate the noise problem. For example, how do we know the CEO giving the presentation hasn't just been using his laptop for three hours on the plane so the battery is run down? You can't just say "use the battery" so the audience doesn't have to endure a whine in the speakers.

As audio engineers, we try to find solutions to technical problems without making the system overly complicated, so it matches the skill level of the users, and meets the needs of the client. In this situation, the goal should be to build the audio system in such a way that it doesn't make noises no matter what computer combination is used. The way to do that is to use a good audio transformer to connect the computer to the mixer.

By the way, Chase hit the nail on the head here.


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## rvhalejr (Aug 31, 2012)

FMEng said:


> ... use a good audio transformer to connect the computer to the mixer...



*!!! SPEC IT SO I CAN TEST IT !!!* Yeah, Sr. Engineers and Scientists want to replicate the solution before giving any credit to the assertion (hypothesis).

BTW I crashed and burned badly with the "good audio transformer" solutions on ebay as the entire genre was yanked as (what I found anyway) they introduced more RF and EMI than they filtered out, not trying to be a pain in the backside just trying the ethereal solution that seems to keep slipping from my grasp.

The solution might be to put the "good audio transformer" inside a shielded well grounded box which would be fine.

I'm tossing in the towel because everything I touch turns to poo. But I would love to reproduce just about any solution anyone comes up with. In another life during the cold war a lot of work was done in 100% metal vaults known as "screen rooms" and EMP resistant devices known as tempest. Mentioned here because it has been
done before but at an astronomical cost. 

All the Best,

Richard


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## FMEng (Aug 31, 2012)

Audio transformers aren't widely used, mass production items these days. Good ones are almost a lost art. They were widely used and understood back in the days of vacuum tube equipment, but not so much now. They are often overlooked because cheap ones create more problems than they solve. But, good ones can make the seemingly impossible work fine. Selecting an appropriate one on eBay is a total crapshoot. Specifications for inferior audio transformers are usually so incomplete that they are meaningless. Go check out the Jensen Transformers web site. There is plenty of information there, all based on good engineering and no hype. Bill Whitlock is legend in the audio community and he literally has written the book on audio transformers. 
WELCOME TO JENSEN TRANSFORMERS, INC.

If you really want to delve into audio noise issues, engineer Neil Muncy coined the term "the pin-1 problem." He wrote some AES papers and gave a number of seminars about noise problems in audio interconnections that stood the audio industry on its head. Today, we have a lot of better audio equipment due to his efforts.
Pin 1 Problem

I'll give you just one, quick example of what transformers can do. My radio station has to feed broadcast quality audio several thousand feet between buildings. The buildings have different AC ground potiential. Using transformers, I can send the audio over exisiting (dry pair) telephone lines, and the results are 20 Hz to 20 kHz, S/N in the 80 dB range and distortion less than 0.1 %. It could not be done using copper cables without transformers. There simply isn't an active balanced input or output stage that would handle the high common-mode voltages between the two buildings.


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## rvhalejr (Sep 1, 2012)

FMEng said:


> I'll give you just one, quick example of what transformers can do. My radio station has to feed broadcast quality audio several thousand feet between buildings. The buildings have different AC ground potiential. Using transformers, I can send the audio over exisiting (dry pair) telephone lines, and the results are 20 Hz to 20 kHz, S/N in the 80 dB range and distortion less than 0.1 %. It could not be done using copper cables without transformers. There simply isn't an active balanced input or output stage that would handle the high common-mode voltages between the two buildings.



I love the citations referenced in the above post, always been a big fan of RLC circuitry, Inductive Coupling, Reflected Impedance and what a few discrete parts can do [1]. 

Nice. However spread spectrum hits 40Mhz using the same copper (my provider who I do not like **&*) and I'm to lazy to give you the spec but its in the management part of the router and partially implemented (about 256 bands if I recall). But this is irrelevant to the problem at hand (Laptop sound noise).

I'm still waiting for someone to post a spec for a solution (part number, circuit, whatever) superior to the Antec one. 

I'm beginning to suspect there is no passive solution for cheap switching power supplies that act like RFI/EMI Transmitters. Sadly I wish there was a cheap old
school "audio transformer" with an op amp or digital circuit that would
work (SPICE2 simulation comes to mind [2]).

Sadly, by the time we come up with any CMRR audio transformer or modern noise cancellation technology it probably will be (A) Impossible for it to work in a digital world and (B) cost a lot more money than the solution already proposed (replace sucky power supplies or buy new systems with noiseless power supplies)

The best I can hope for is the niche created by Antec will spread in applicability and profitability such that major player's will jump in with both feet.

Sadly, here we have lots of wishful thinking, no solid test case (IEEE/IEC/NIST/NBS/etc.) to validate a solution if one were proposed even though
RLC circuits are well understood.[3] 

As a society we have dumbed down to the point that when a working technical solution does exist there are social, physiological reasons why what obviously already works (DAWs in recording and stage performance) will, in the minds of some, just not cut it. 

For Home Recording and Performer Wanna-bees (Me) Antec should benefit financially from their work (free market at work I'd propose).

Perhaps most others not. Regardless I love your effort and thought that you have given to this thread.

Best of Luck to everyone and Thanks...

Richard 


Notes
[1] sengpielaudio.com/calculator-timeconstant.htm
[2] en.wikipedia.org/wiki/SPICE
[3] en.wikipedia.org/wiki/Transfer_function -- Potentially lots of useful filters mentioned which might be leveraged.


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## llecount (Sep 11, 2012)

FMEng said:


> In the most recent scenario discussed here, it's a conference room or meeting hall, where we have no control over who is bringing in what computer. There may be no technical supervision. The solution has to be simple to untrained users and universal to any computer carried into the room. A solution that works fine in a controlled environment, like a theater control booth, studio, or home doesn't apply here.




chausman said:


> That, is the problem. In one year at my high school, we've had everything from laptops running Windows 2000, to 2012 MacBook Airs, and everything in between. With people who just learned how to use PowerPoint for that event, to people who have years of experience. There is no way I could say (You just need to log in remotely, and connect to your computer, and then mine will actually supply the audio.




FMEng said:


> I guess my point is being missed here. There aren't too many situations where we can dictate to run on battery only, use only a certain brand of power supply, use a different computer, stand on your head and cough, to eliminate the noise problem. For example, how do we know the CEO giving the presentation hasn't just been using his laptop for three hours on the plane so the battery is run down? You can't just say "use the battery" so the audience doesn't have to endure a whine in the speakers.
> 
> As audio engineers, we try to find solutions to technical problems without making the system overly complicated, so it matches the skill level of the users, and meets the needs of the client. In this situation, the goal should be to build the audio system in such a way that it doesn't make noises no matter what computer combination is used. The way to do that is to use a good audio transformer to connect the computer to the mixer.



EXACTLY! The systems in our rooms should just "work", no fiddling, no extra changes.. Just work as it should. If I was in the client's shoes, that is precisely what I would expect. 
If there is no *safe* way of fixing this problem, then my only other solution I see would be to look in to a USB device.. But ONLY if it automatically installs itself on any modern version of Windows (XP-W7) or Mac OS. I've never looked to see if such a device exists.. If they are fairly inexpensive, I'd be willing to buy one and give it a try, just to see how it works in this situation. Though I'm afraid it'll just be another piece that would accidentally grow legs and walk off eventually.


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## ruinexplorer (Mar 9, 2013)

Thread back from the dead. I just saw an announcement that Radial engineering has come up with a new direct box to reduce the laptop noise. So, if anyone happens to pick one up, it would be nice to know the results.


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## DrPinto (Mar 9, 2013)

ruinexplorer said:


> Thread back from the dead. I just saw an announcement that Radial engineering has come up with a new direct box to reduce the laptop noise. So, if anyone happens to pick one up, it would be nice to know the results.



Looks like just a passive DI with a permanent thin cable attached. Doesn't sound like a good idea. So what happens when the cable goes bad?

I have the Radial ProAv1 and love it. At first look, I can't see any benefit of the new DI box.


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## Novo63 (Apr 2, 2013)

Newbie here but I have two old laptops, Asus brand. One power supply makes the terrible noise and one does not. In the same set up, other peoples' laptop supplies have made the terrible noise as well. Has anyone thought of checking the house power?

Two cents or less

Novo63

great posts though.


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## AudJ (Apr 2, 2013)

Admittedly, I'm not sure if anyone else might have suggested already, but are all the power outlets (receptacles) in your venue wired correctly? A simple test can relieve some headaches. 

Check fluorecent usage?

Also, I have heard that weird problems with grounding can sometimes be avoided by choosing power for the sound system off the same side of the breaker box, if it is possible. I have never confirmed this notion however.

I ditched the laptop I was given, and now use my own Mac for this purpose...


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## museav (Apr 3, 2013)

AudJ said:


> Admittedly, I'm not sure if anyone else might have suggested already, but are all the power outlets (receptacles) in your venue wired correctly? A simple test can relieve some headaches.


A simple test may identify some wiring problems but others may require more advanced testing gear and/or greater effort. Not a bad idea to always check the power with something like IDEAL INDUSTRIES, INC. - E-Z Check® Circuit Testers, but a tool like IDEAL INDUSTRIES, INC. - SureTest® Circuit Analyzers can provide much more information for troubleshooting.


AudJ said:


> Also, I have heard that weird problems with grounding can sometimes be avoided by choosing power for the sound system off the same side of the breaker box, if it is possible. I have never confirmed this notion however.


http://www.middleatlantic.com/pdf/PowerPaper.pdf
http://www.surgex.com/pdf/PowerGround.pdf


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