Electrical noise from laptop headphone jack. [Archive]

BaconPie

02-27-2009, 03:56 PM

After my parents bought a new surround sound system I was quick on the ball to secure the old one for my room. I've had it hooked up to my PS3 and laptop for a while now but mostly just use it with the PS3 and play the laptops sound out of the laptops built in speakers.

When I do use it with my laptop i've got it connected using an audio cable that connects with RCA like plugs into the back of the surround sound and the laptops 3.5mm headphone jack.

http://www.ust.hk/itsc/classroom/notebook/photo/cable_audio_pc.jpg

I use my laptop at my desk almost all of the time (It was a Christmas present a few years ago and i'm not building a PC until I can justify the price) and as such always have the power cable plugged in.

My problem is that whenever I have the laptop plugged into the surround sound and its power cable is in I get this god awful electrical sounding squeal from the speakers. If I turn up the volume its not noticeable but when the music goes off all I can hear is: "EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE".

Very annoying.

It makes no sound when the power cable isn't in but the battery life isn't great so this isn't very ideal. Does anyone have any solutions or ideas on how to fix this?

toraton

02-27-2009, 05:02 PM

Sounds like a bad ground. Probably no easy way to fix short of soldering.

MunkeyQ

02-27-2009, 05:21 PM

My old Dell had the same problem. I'm pretty sure it's the combination of a very noisy switching power supply and bad grounding since Dell use a weird floating ground.

The solution is to engage the ground lift switch on your stereo in the off-chance it has one, which will reduce the noise. However, mostly pro/expensive stuff has this feature so chances are you haven't got it. Don't remove the ground if it hasn't got a switch as that could be dangerous.

However, the solution I used is to get a quality external sound card which has better shielding and grounding. That meant I didn't have to lift the ground, and you get blissful silence.

BaconPie

02-27-2009, 05:46 PM

I was just reading some more into the situation and it appears that the low frequencies of the power supply, like you said, can be blocked off with a capacitor or something. Do you think there might be a DIY way to get this sorted?

Edit: Just found this: http://www.elantraxd.com/forums/showthread.php?t=21066 Nothing to do with a capacitor and it seems very simple. Might give it a try.

The external sound card idea sounds good too. I'm no super audiophile but I know i'm more pedantic than my friends when it comes to sound quality. Would the external sound card provide much of a better quality in sound?

Also, if I did buy an external sound card then i'd have to buy a USB dock. The laptop has four USB ports, two at the back and two in the side. The two in the back are used for my mouse and External HDD and the ones in the sides are for memory pens and temporary stuff because they just get in the way. Would running it through a USB dock be a problem do you think?

phmeworp

02-27-2009, 06:33 PM

I am going to go, in part, with MunkeyQ's first paragraph: It is the noisy power supply/charger. But it really is not a ground-loop issue. The link you found will most likely provide no relief at all, but it looks cheap and simple, so by all means give it a try if you like. The whole ground-loop issue could easily take up an entire thread.

The switching chargers are very light-weight and extremely efficient, but also insanely noisy. Computers don't really mind the noise, after all PC's run on noise (high-frequency wide-band square waves of digital energy) but that noise does not go so well with audio applications.

This may sound stupid and may have slim to zero chance of helping, but even easier and faster than the ground-loop fix: Try reversing the power plug on your charger (remove from outlet, spin 180 degrees and re-insert).

The next best approach, IMHO, would be to try an inline LC filter for the charger. This might not be for the faint of heart, but probable a better approach than getting a linear power supply (with good filtering) to replace that nasty switcher.

As an after thought... how old is the battery on your laptop? You mention that it does not hold a charge very long. If it has grown weak, its internal impedance may have gone up significantly, thus providing less filtering action.

BaconPie

02-28-2009, 10:18 AM

The link you found will most likely provide no relief at all, but it looks cheap and simple, so by all means give it a try if you like.

You where right, it never worked. :p

This may sound stupid and may have slim to zero chance of helping, but even easier and faster than the ground-loop fix: Try reversing the power plug on your charger (remove from outlet, spin 180 degrees and re-insert).

I live in the UK and everything has three prongs here so, unfortunately, its not as simple as just twisting it around.

As an after thought... how old is the battery on your laptop? You mention that it does not hold a charge very long. If it has grown weak, its internal impedance may have gone up significantly, thus providing less filtering action.

It's just over two years old. When I say it doesn't hold a charge for very long I mean not long enough. It's about 1 hour on full power and I can squeeze about 2-3 hours from it if I run it on bare minimum. I don't really use it as a portable so the battery doesn't get much use at all, its mainly plugged into the wall so unless its been battered by age then I don't think there is anything wrong with it.

I think I might try the External Sound Card fix, it seems the simplest. Would a £10 one from eBay suffice or am I going to have to shell out?

Thanks for the reply's by the way. :thumbsup:

BananaFuck

03-03-2009, 12:18 AM

It is most likely a ground-loop problem. I would remove the ground on the stereo's power plug, but it isn't the greatest thing to do... You might want to remove the battery from your laptop, and just run it straight from the charger.

BaconPie

03-03-2009, 06:52 PM

You might want to remove the battery from your laptop, and just run it straight from the charger.

It's the charger that is causing the problem.

MunkeyQ

03-04-2009, 12:56 AM

hazmat

03-04-2009, 02:52 PM

I can hear is: "EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE".

Youre actually hearing FFFFFF.

BaconPie

03-04-2009, 08:28 PM

Youre actually hearing FFFFFF.

Where can you upload sounds to the internet? Something quick like ImageShack only for sounds.

I've just recorded it the sound you see, and its defiantly an EEEEEEEEEEEEEEEEEEEE, with a mild fuzz to it.

phmeworp

03-04-2009, 09:58 PM

Your drunken mod replying here. Will reply with a more sober thing in the morn.

Anyway, the switching power supply is causing the problem. A ground loop causes a hum, not noise. Improper earthing fails to attenuate the noise.

If that is your drunken reply, you do NOT know how to get properly drunk! That was a very sober and sound reply.

Where can you upload sounds to the internet? Something quick like ImageShack only for sounds.

I've just recorded it the sound you see, and its defiantly an EEEEEEEEEEEEEEEEEEEE, with a mild fuzz to it.

Thanks, a good hear is worth a thousand words. It enabled me to solve a major mystery in TFTT a while ago.

BaconPie

03-04-2009, 10:23 PM

http://rapidshare.com/files/205419359/Recording.mp3.html

I rapidshared it. It'll be down in a few days so if its not there just ask me and i'll up it again.

HLC

03-04-2009, 11:11 PM

Isn't there a good chance an external sound card is going to catch and amplify the same artifact from the power supply?

phmeworp

03-04-2009, 11:14 PM

Dude!!! Thanks for providing that. Remind me to thank you and rep you.

If only folks could submit that kind of info, it would be soooo much easier to help out friends in need. Yeah, it was a bit difficult to hear at first, but after playing it out a few dozen times...

The constant 'squeal' in the background was unmistakenably power supply noise. The semi-background clicking and buzzing was from your PC.

Is there any way you could, using the identical setup and settings make a similar recording with the ONLY difference being with the power supply/charger not connected?

If you change anything other than the power conection, the 'test' will be invalid,.

Thanks!!!

phmeworp

03-04-2009, 11:16 PM

Isn't there a good chance an external sound card is going to catch and amplify the same artifact from the power supply?

Yeah, that became somewhat my thoughts as well. Lets let the test go on and decide from there where the real problem lies. ???

MunkeyQ

03-04-2009, 11:19 PM

Isn't there a good chance an external sound card is going to catch and amplify the same artifact from the power supply?
In my experience, this isn't the case - decent external cards have a different power supply, so they're not affected by the noise present on the 5v line. (assuming it's a USB card).

My Dell was very, very, noisy using the built-in card, but an external Creative completely silenced it.

And yep, that squeal reeks of nasty switching power supply noise.

hazmat

03-04-2009, 11:25 PM

I've just recorded it the sound you see, and its defiantly an EEEEEEEEEEEEEEEEEEEE, with a mild fuzz to it.

Eh it was a joke. If you were to put the loudest possible sound into hex... it would be F's.

BaconPie

03-05-2009, 12:02 AM

Eh it was a joke. If you were to put the loudest possible sound into hex... it would be F's.

I can't believe I missed that. Damn.

I'll record the other thing tomorrow, its late now. Thanks for the inputs again!

BaconPie

03-05-2009, 12:53 PM

Here you go:

Without Power Cord: http://rapidshare.com/files/205635575/Without_Power.mp3.html
(I've played music at intervals so you know its coming from the speakers.)

With Power Cord: http://rapidshare.com/files/205635576/WithPower.mp3.html
(I've also played music on this one for comparison.)

BaconPie

03-29-2009, 07:39 PM

Hey, its me again.

I still havn't got this damn noise fixed. I bought a shitty 99p USB external sound card from ebay and that never solved the problem but for 99p I wasn't expecting it too! :p

The urge to put my music on my speakers has come back and just now I covered up the ground on my laptops AC plug with some electrical tape and it silenced the squeal. That's not a permanent fix though; covering up the ground is baaaad news.

I also checked out the ground on the surround sound only to find out its made from plastic! I opened up the plug and inside is a US style plug! Pretty ghetto if you ask me:

http://img24.imageshack.us/img24/8441/dsc01396m.jpg

Also, there is a small plug in the back of the unit that has a ground symbol (I think its a variation of the proper one) on it.

http://img7.imageshack.us/img7/349/dsc01397y.jpg

I tried rigging it to the ground plugs using some speaker wire but that fell right on its face.

So, yeah, any more ideas? (Apart from shell out on an expensive external sound card. Or is this my only hope?)

Jaguarstrike

03-30-2009, 02:25 PM

BaconPie

03-30-2009, 09:14 PM

Have you tried a ground-loop isolator?

http://www.radioshack.com/product/index.jsp?productId=2062214

If it doesnt work as touted on the site or the box, you can just return it. People who work at radioshack hate radioshack.

Edit:

Rather than covering up the ground on your laptop, why not just wire the ground pins of the stereo and the laptop together?

I live in the UK so no radio shack for me. There is eBay or Maplin though; the latter being incredibly over priced.

Also, the stereo doesn't have a ground pin. There's a picture in my previous post showing that its just a two pin US style plug in a UK housing. So the ground on it is just false.

If you mean wire the ground looking hole from the stereo to the ground on my laptop then yeah, i've tried that and it never worked either.

Also, they're both connected into an extension cord with multiple sockets. I'm not sure on the specifics but i'm pretty sure all the grounds are connected in that anyway.

Also, before anyone asks, i've tried the plugs in different sockets and directly to a wall. The problem still persists.

I'll defiantly check out the ground loop isolator though. Thanks. :thumbsup:

MunkeyQ

03-30-2009, 11:55 PM

For double-insulated things, you don't need a ground hence the plastic ground pin. It's completely normal practice, but it can cause problems because the ground "floats". The reason it isn't left off completely is because the socket needs ground to be inserted first for the little hatches over the live/neutral pins will open.

What Jaguarstrike posted is an isolation transformer - basically a 1:1 winding transformer with impedances to match what the devices should see. The cheap ones aren't too great but you may not notice the difference in sound quality. Typically, treble becomes less defined and a bit of very low bass disappears as the transfomer loses efficiency down low. The pro units are good though.

That symbol on the back is for an antenna groundplane, which is completely different to an audio or power ground. You should also never, ever run a seperate ground by joining pins whilst a ground still exists in the wall via an unknown route as it can cause a nasty fire. The slight differences in potential can sometimes cause a current of hundreds of amps (at a very low voltage) to build up and burn things.

In short: don't join grounds, buy an isolation transformer as Jag suggested. Ebay is good for this.

phmeworp

03-31-2009, 01:55 AM

BaconPie: Congratulations... you solved your own problem.

I would have gotten back to you sooner, but it took a bit longer to wipe the egg off of my face than I would have ever expected. I have been thinking about this issue ever since you first posted and realized that it could have actually been a ground loop issue, even though the symptoms were not consistent with traditional such situations.

There are any number of different 'fixes' for your problem that would meet with the wide variety of governmental and safety regulations that have been laid down over the years, but the 'fix' you have experimentally discovered is the simplest and most cost effective one yet.

Unless you plan on running around the yard barefoot or planting your headphones on either side of your brain whilst soaking in the tub, you are most likely 99.99% safe in just keeping your laptop ground plug wrapped in electrical tape. One word of caution: In the event of a direct lightning srike, it will provide you little protection.... but then again, nothing else will.

If you were not so far away, I'd stil like to come to your home with a digital storage scope and a spectrum analysier to see exactly where/how the true problem arises and find a 'legitmate' fix to it.

Thanks!

BaconPie

04-03-2009, 08:51 PM

Sorry to bump the thread again but I thought i'd give some closure and maybe help someone in the future with the same problem.

The Ground Loop Isolator (http://www.radioshack.com/product/index.jsp?productId=2062214) solved the problem! WooHoo! (I got it from eBay for like £4.)

I haven't fully checked the sound quality yet but any sort of sequel is completely gone. Thanks to all that helped. :thumbsup: