Laptop audio cable buzz noise - Canadian TV, Computing and Home Theatre Forums

wahboy · 2010-02-12, 10:53 AM

Hi there,

I connect my laptop to my HDTV through VGA cable for video and a 3.5mm stereo cable for audio. The problem I'm facing now is there is this buzz noise from the TV speaker whenever the Laptop's harddrive is loading/running. It's kinda annoying when you're watching movies especially during quiet scenes.

Is there any quick fix to get rid of the buzz noise? Where exactly the problem is? The laptop audio jack, the 3.5mm cable, or the TV??

Thank you in advance for your advice.

joudbren · 2010-02-13, 10:39 AM

Is the laptop plugged into AC power when this happens? If so does your AC power adaptor have a ground plug or just the two blades for AC?

It sounds like a ground loop problem but hard to say. Some laptops/PC's are just noisy electronically. Check out the following links for ideas. Cheers!

http://www.epanorama.net/documents/g...e_solving.html

James

wahboy · 2010-02-16, 09:16 AM

Thanks James. You're exactly right! I found out that the buzz noise disappeared when I disconnect the AC power source from the laptop. But I believe the AC adapter has the ground plug cause it has three legs instead of two.

I read the link you provided and the solution is to put an isolator or transformer in between the TV and the audio source. I haven't tried looking for one yet, but sounds like it will cost me at least $60.

Jake · 2010-02-16, 09:32 AM

You would be better off sending digital audio (coax) to the TV (if equipped) or receiver. It will not be affected by the interference. Most modern laptops can output digital audio from the 3.5mm jack. You just need a $5 adapter that has a mini-jack on one end and a female RCA jack on the other. You most likely already have an RCA cable.

http://www.tvcables.co.uk/images/ite...ca-adapter.jpg

It is possible your stereo cable will work. Just plug the red end into the receiver's COAX AUDIO input and if not try the white.

wahboy · 2010-02-16, 03:01 PM

I believe my TV will only accept 3.5mm audio-in if I'm connecting my laptop through the VGA slot, but I will verify it tonight when I'm back home. Also, I don't have a receiver connected in the system, therefore, I will have to rely on what's available at the back panel of my TV.

Do I need special cable for the digital coax audio or a typical RCA cable will work?

Thanks Jake for your advice.

Jake · 2010-02-16, 03:37 PM

If your TV is low-end or old I doubt it will have a digital input. And if it does it will most likely be optical. If on the odd chance it does have a coax input just about any average quality RCA cable will work.

Apkerr · 2010-02-18, 11:54 PM

True "ground loops" happen when you have two components of a system that have different electric potential on their ground pins. When these components are connected with a cable that is using the ground on both sides, the difference in potential causes a current to flow. That current produces a characteristic hum that anyone who has worked a pro audio system knows and dreads (and has probably spent hours trying to trace and fix). This hum would be constant as soon as you plug the audio cable in, and would not vary with computer activity.

Since your noise problem happens when the hard disk is revving up, and presumably not when the computer is sitting idle, it is not a ground loop. It is probably noise being generated by the power supply that is being transferred into the audio circuitry due to poor component placement or inadequate internal sheilding.

Now, even though it isn't a ground loop, exactly, some of the fixes for ground loops may be helpful. You mentioned that your power supply has three prongs. No matter what you read on the internet, DO NOT cut off the ground prong or use a cheater plug. Instead, see if your laptop manufacturer makes a two-prong version. Most of these power supplies don't really need a ground prong, but that's not for you or I to decide.

An isolation transformer or "direct injection" box might help. If you have a professional audio store nearby (especially one with a recording studio), take your laptop in and have someone help you try a few things. There are DI boxes designed specifically for connecting laptops and other consumer gear to professional audio systems. Be aware, however, that a high quality device with a good transformer is quite expensive. Make sure they understand that this is to connect to a TV, so that the device has the proper outputs...I've never seen a TV with balanced XLR inputs, for example.

There are also some simple things to check. Move the power supply around and see if the sound changes. Check the audio mixer settings on your laptop and make sure that the microphone input is muted. I've heard of noise getting picked up by the microphone circuitry and amplified, even when there wasn't a mic plugged in.

Don't get talked into buying any hocus pocus gizmos without being able to try them first, or at least having a good refund policy. It's possible that your laptop is simply noisy due to poor design and can't be fixed.

Good luck.

2010-02-12, 10:53 AM	#1
wahboy Rookie Join Date: Aug 2009 Posts: 8	Laptop audio cable buzz noise Hi there, I connect my laptop to my HDTV through VGA cable for video and a 3.5mm stereo cable for audio. The problem I'm facing now is there is this buzz noise from the TV speaker whenever the Laptop's harddrive is loading/running. It's kinda annoying when you're watching movies especially during quiet scenes. Is there any quick fix to get rid of the buzz noise? Where exactly the problem is? The laptop audio jack, the 3.5mm cable, or the TV?? Thank you in advance for your advice.

2010-02-16, 09:32 AM	#4
Jake Moderator Join Date: Apr 2003 Location: Gatineau and Ottawa Posts: 10,238	You would be better off sending digital audio (coax) to the TV (if equipped) or receiver. It will not be affected by the interference. Most modern laptops can output digital audio from the 3.5mm jack. You just need a $5 adapter that has a mini-jack on one end and a female RCA jack on the other. You most likely already have an RCA cable. http://www.tvcables.co.uk/images/ite...ca-adapter.jpg It is possible your stereo cable will work. Just plug the red end into the receiver's COAX AUDIO input and if not try the white. __________________ Tip: See an offending post? Don't reply, report it by clicking on the 'Report Post' icon.

2010-02-16, 03:37 PM	#6
Jake Moderator Join Date: Apr 2003 Location: Gatineau and Ottawa Posts: 10,238	If your TV is low-end or old I doubt it will have a digital input. And if it does it will most likely be optical. If on the odd chance it does have a coax input just about any average quality RCA cable will work. __________________ Tip: See an offending post? Don't reply, report it by clicking on the 'Report Post' icon.

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2010-02-13, 10:39 AM	#2
joudbren Join Date: Jan 2007 Location: Edmonton, Alberta Posts: 145	Is the laptop plugged into AC power when this happens? If so does your AC power adaptor have a ground plug or just the two blades for AC? It sounds like a ground loop problem but hard to say. Some laptops/PC's are just noisy electronically. Check out the following links for ideas. Cheers! http://www.epanorama.net/documents/g...e_solving.html James

2010-02-16, 09:16 AM	#3
wahboy Rookie Join Date: Aug 2009 Posts: 8	Thanks James. You're exactly right! I found out that the buzz noise disappeared when I disconnect the AC power source from the laptop. But I believe the AC adapter has the ground plug cause it has three legs instead of two. I read the link you provided and the solution is to put an isolator or transformer in between the TV and the audio source. I haven't tried looking for one yet, but sounds like it will cost me at least $60.

2010-02-16, 03:01 PM	#5
wahboy Rookie Join Date: Aug 2009 Posts: 8	I believe my TV will only accept 3.5mm audio-in if I'm connecting my laptop through the VGA slot, but I will verify it tonight when I'm back home. Also, I don't have a receiver connected in the system, therefore, I will have to rely on what's available at the back panel of my TV. Do I need special cable for the digital coax audio or a typical RCA cable will work? Thanks Jake for your advice.

2010-02-18, 11:54 PM	#7
Apkerr Join Date: Aug 2005 Posts: 20	True "ground loops" happen when you have two components of a system that have different electric potential on their ground pins. When these components are connected with a cable that is using the ground on both sides, the difference in potential causes a current to flow. That current produces a characteristic hum that anyone who has worked a pro audio system knows and dreads (and has probably spent hours trying to trace and fix). This hum would be constant as soon as you plug the audio cable in, and would not vary with computer activity. Since your noise problem happens when the hard disk is revving up, and presumably not when the computer is sitting idle, it is not a ground loop. It is probably noise being generated by the power supply that is being transferred into the audio circuitry due to poor component placement or inadequate internal sheilding. Now, even though it isn't a ground loop, exactly, some of the fixes for ground loops may be helpful. You mentioned that your power supply has three prongs. No matter what you read on the internet, DO NOT cut off the ground prong or use a cheater plug. Instead, see if your laptop manufacturer makes a two-prong version. Most of these power supplies don't really need a ground prong, but that's not for you or I to decide. An isolation transformer or "direct injection" box might help. If you have a professional audio store nearby (especially one with a recording studio), take your laptop in and have someone help you try a few things. There are DI boxes designed specifically for connecting laptops and other consumer gear to professional audio systems. Be aware, however, that a high quality device with a good transformer is quite expensive. Make sure they understand that this is to connect to a TV, so that the device has the proper outputs...I've never seen a TV with balanced XLR inputs, for example. There are also some simple things to check. Move the power supply around and see if the sound changes. Check the audio mixer settings on your laptop and make sure that the microphone input is muted. I've heard of noise getting picked up by the microphone circuitry and amplified, even when there wasn't a mic plugged in. Don't get talked into buying any hocus pocus gizmos without being able to try them first, or at least having a good refund policy. It's possible that your laptop is simply noisy due to poor design and can't be fixed. Good luck.