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Noise from Sound Port on Computer


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I am connecting the sound output (earphone connection) on my laptop to a Yamaha mixer board then to a 100 Watt amp. I am getting some scratchy noise not terribly loud but irritating none the less. I have tried a different cable and several different volume levels, and then I connected the same system to my desktop and did not get the noise so I know it is with the laptop computer. Has anyone ever encountered this and how did you fix it?

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Most headphone outputs on laptops are not the best. If the noise is a contanst hum or buzzing noise, you may be able to use a ground loop isolator to get rid of the noise. But you will also have to get a few adapters fro go from the 1/8 Headphone phono to RCA but if you are plugging it into your Mixer anyway that has RCA plugs, you should be able to just put it inline.

You can find this at walmart in the car audio dept.

http://www.tinyurl.com/yas73f



0003399155034_500X500.jpg

If that is not the problem, you may want to buy a USB Audio Device. It is pretty much an external sound card that connects to your computer via USB. This way you don't even use the sound port on your computer.

You can pick them up as cheap as $20 or more for higher quality ones.


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If the problem exists when you aren't touching anything, then you can rule out a connection problem. If you can get the noise to correspond to you moving the laptop, amp or the cables in between, then you have a connector problem.

If the noise is constant, even when you aren't touching anything, you probably have a ground loop problem. We call it the "60 Hz buzz". I would try the following (1) make sure that the mixer and the amp are plugged into the same circuit. (2) You can try using a ground lift plug on the amp and/or mixer - they are the grey adapters that you plug a grounded three-prong plug into but they only have two prongs where you plug them in the wall. If you do this, make sure that the equipment is inside and away from any moisture as you are eliminating the protection of the grounding connection.

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I have a ground lift connection on the amp and it seems to help some but not much. If I were to go with the USB sound adapter would it affect the speed of my USB to my LOR controllers?

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Mr. Griswold wrote:

I have a ground lift connection on the amp and it seems to help some but not much. If I were to go with the USB sound adapter would it affect the speed of my USB to my LOR controllers?

I don't think it would. You may run into an issue if your laptop only has one USB port and you have to use a USB hub to plug in the LOR USR controller and the USB sound card. If you can plug both devices right into your laptop, you should not have a problem.

-Richard
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Mr. Griswold wrote:

I am getting some scratchy noise not terribly loud but irritating none the less.


I had this occur on one notebook and I found that it was coming from the microphone input. The solution was to mute the microphone input in the driver. Just double click on the speaker in the tray and click mute under the microphone slider.

Note: You may need to open the options menu and make the microphone slider visible.
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Thanks for advising on the microphone, tried it but still get annoying hum. I am looking at the usb sound devises on ebay and I see several for under $5-10, looks like little memory sticks with a speaker connection will this work ok?

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My closest friend is a DJ that uses his laptop to play all MP3s using PCDJ Red. After changing mixers, he had the same irritating noise. With a high power amp and studio monitors, it was amplified to an annoying volume even when the music was turned up. He brought the entire system over one day and we troubleshot it until we found the source of the noise. When I put a ground isolator (the little grey piece the drops the gound pin) on the laptop power supply, the noise went completely away. That ground goes to the metal case inside the laptop power supply. How that created the noise is beyond me, but after 3 hours of trying different things including making all new cables I was very happy when we figured it out. The thing that made me try isolating the ground was, when I unplugged the power supply it went away.

Give it a try... You might have the same problem.

jeff

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Thanks that is where the noise is coming from. I reduced 98% of the noise in the output by unplugging the outlet. I will have to get an adapter tomorrow to try. Sounds alot better like that though.

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Yes for 98 cents at lowes you can get a little gray adapter that will fix you right up. I also dj and this fixes my problems as well.

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I beg you not to defeat the safety ground connection on the AC outlet. Remember we are dealing with power that is dangerous. If you defeat the safety ground, you are putting yourself at risk.

I work for a major professional audio manufacturer. I am very aware of ground loops and how they are actually caused. But, that book of information is too much for this thread.

One of the easiest ways to stop the ground loop, but not reduce your safety is to use a 1:1 transformer between the computer and the mixer. A 1:1 (also called 600:600 ohm) transformer can be found at Markertek.com

See the following link:

http://www.epanorama.net/documents/groundloop/

Cheers,

Rick Waller

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The only thing the ground wire on a Laptop power supply protects is the metal frame inside the plastic power supply case. As long as there the case is in tact, it is no different than a double insulated tool. There is no reason to be alarmed in defeating the ground pin on one of these power supplies. Just be sure not to get it wet, as that is really the only reason for the ground...

jeff

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As an Electrical Engineer, I disagree. It is true that under correct, normal operating conditions, the ground wire only protects the metal frame in the power supply. But what happens when something goes wrong? What happens when a wire inside becomes loose, or a componen t inside becomes loose? While the odds of this happening is small, there is still a possibility. When wires or components come loose, they bridge things that we did not intend for them to bridge, thus the purpose of the safety ground. While the odds of this happening are slim, the odds of a fire happening at your house are also slim, but you still have fire insurance, right? How much is your life worth? How much risk to you want to take with your life?

And remember, since the mixer is connected to the laptop via copper, it's possible that the metal case of the mixer would become energized to 120v. Yes, I've seen this occur before. I've also seen several guitar amps go bad, where the strings on the guitar are now energized at 120v. It's very scarry when the guitar player touches the properly grounded mic and gets a shock.

Please, do NOT defeat the safety grounds. They are there to protect you. But, it is your risk, so take as much risk as you would like. I would prefer to instruct people on the correct and safe way to break a ground loop.

Cheers.

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I'm not going to debate the ground safety issue. This is a common and known problem among DJs. Half of the laptop power supplies don't even have a ground. You can either take responsibility for your own safety, or find a power supply without a ground pin. As a Relay Technician for the most reliable power company in the country, I defeat the ground pin on test equipment all the time, as some relay testing requires it. You cannot have a ground return path in 26KV line/distance testing. So you use a ground eliminator and work carefully. We all know that electricity is dangerous.

You have your opinion of what is right and wrong, and I have my own. Let the guy that has the static on his DJ equipment decide if he is safe enough defeating his Laptop power supply ground (like the half-million other DJs across the globe do)

jeff:(

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As an electrical engineer I agree/disagree with Opie. I believe the problem actually occurs when power supply designers, attach the case ground to the DC ground of the power supply output if this were not the case then there would be no ground loop to have a problem with. Most AC to DC power supplies have a transformer, rectifier and then some sort of regulation the AC ground can connect to the case of the power supply just fine and sometimes designers connect the case ground to the DC ground on the output of the rectifier this is where the problem comes in, due to the fact that most laptops only have two pins on thier power supply inputs some have 3 but that doesn't necessarily mean that one is grounded. I agree with the fact that we want some sort of circuit protection. I also disagree that we need a direct grounded case on the laptop itself.

Scenario 1: Grounded power supply ungrounded laptop case. laptop gets stepped on shorting out something in the laptop worst that can happen is 12-19 volts gets somewhere you don't want it. Result most likely Dead laptop, Fuse blows in power supply. there would be no change in this scenario if the laptop case were grounded.

Scenario 2 same grounding scheme as 1. Now lets step on the Power supply, Lets say for a breif moment before 120vac gets grounded to the case 120vac gets through the PSU to the laptop, most of the laptop circuitry gets burned, and the power supply might blow its fuse then the house circuit breaker trips.

Scenario 3: Lets ground the Laptop and step on the power supply, Most like the same scenario will occur due to the fact that that a momentary spike could still occur on the laptop killing some circuitry there.

Now I do disagree with others in the thread about disconnecting the ground from the outlet to the PSU, but disconnecting the Grounding of the ground to the dc ground is where I would accept the "Lifting" of the ground. This would get rid of the ground loop problem without having to resort to trasformers in the audio line.

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Mr. Griswold wrote:

Thanks that is where the noise is coming from. I reduced 98% of the noise in the output by unplugging the outlet. I will have to get an adapter tomorrow to try. Sounds alot better like that though.

Something else to remember in eliminating as much of background hum as possible is to raise the output volume of the laptop as high as is practical without distortion. This will require that you turn the gain down on the channel you are using on the mixer.

This will have the effect of increasing the effective music-to-noise ratio. If your laptop is producing 3dB as an output and you are boosting that with the mixer and amp, introducing 3dB of noise will be immediately noticeable. If your laptop is producing music at 18dB, 3dB of noise will likely not be noticeable.
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Yes I did notice that running the laptop volume at max and then controlling the mixer volume reduces a lot of noise to the bearable level. I went ahead and purchased a Creative Labs Sound Blaster external USB sound card to try also, I picked it up for 31.00 on eBay. I appreciate all of the help I have gotten on this thread. I have always wanted to sit down and get the noise out of the amp anyway because I never could use my Band-in-a-Box software on the laptop because of it just never took time to sit down and figure it out. I should get my LOR hardware in tomorrow I am very excited, I have been able to get 5 songs done, thanks on 2 of them to LOR posting premade sequences that I was able to quickly modify. I posted one on LORsequences.com yesterday for Manheim steamroller "Carol of the Bells" if anyone is interested in checking a real newbie's work.....

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I would have recommended the USB devices by M-Audio, Tapco, or many other pro audio manufacturers. Then you would have had either a balanced XLR or balanced 1/4" to connect to the Yamaha. They would supply much better audio than any Creative Audio device. Of course, they do cost more, as well.

Cheers,

Rick Waller

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