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Computer Hum

Printed From: Speakerplans.com
Category: Other Chat
Forum Name: Computer Talk
Forum Description: Help and discussion about your manly PC or girly Mac
URL: https://forum.speakerplans.com/forum_posts.asp?TID=74660
Printed Date: 29 March 2024 at 2:48pm
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com


Topic: Computer Hum
Posted By: Audio_AL
Subject: Computer Hum
Date Posted: 22 December 2012 at 3:17am
As the title suggests I've got a laptop that makes a terrible hum when I am playing music threw it into my system. Its not there when I don't have the power cable plugged in so it must be some kind of a ground loop or something? The hum was still there when I plugged the power cord into my power conditioner. Is there anything I can do to kill the noise? Thanks!


Furman M-8Lx Power Conditioner

http://www.parts-express.com/pe/showdetl.cfm?partnumber=248-784


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Make it loud!



Replies:
Posted By: b grade
Date Posted: 22 December 2012 at 3:30am
edit- removed suggestion


Posted By: specialjustin
Date Posted: 22 December 2012 at 4:04am
Get a soundcard?


Posted By: b grade
Date Posted: 22 December 2012 at 4:05am
I have known plenty of people who still had that problem with an external soundcard.


Posted By: shagnasty
Date Posted: 22 December 2012 at 4:37am
Much as I would never mains ground lift, anyone who does is a fycking moron, you have a ground loop issue, try and buy a 2 wire psu or use something like berry uca202 via optical, you'll find your hum disappears on battery, poss use an isolating transformer on your mains in, but never ground lift mains anywhere on an audio rig


Posted By: b grade
Date Posted: 22 December 2012 at 5:16am
Sorry if my advice sounds moronic.  I just know it is a cheap fix and I have seen it work.  I would never have thought of it, because I would never lift a ground on PA gear either.


Posted By: shagnasty
Date Posted: 22 December 2012 at 5:24am
It is not your advice is moronic, the Op is in the US and you guys have pussy-assed mains, but the point is you have ground for a reason and you guys don't use RCDs outside the bathroom as far as I can see.
 
The stage is massively high hazzard space, loads of good ground (earth) points and sweaty hands, just using a gound lifter is no a good plan, even 120V will kill if it lands in the wrong place....
 
I always seem harsh on here, but I have toured the world and seen stuff that would shave your ball sack, you don't wanna do that unless you are ready!!!Smile
 
I've had probs with my Tecra and a few Dells with ground hum the UCA202 works if you can get a digital in or find a 2 wire PSU (not a "modded" 3wire) but don't assume it's OK, because dead people clutter up the stage!!!!


Posted By: TENSiON
Date Posted: 22 December 2012 at 9:09am
That's usual with most crappy laptop PSU's..

And the holy grail of all solutions: a ground-loop isolator (transformer decoupler)!

Really works wonders, and plenty of it around once you know what you are looking for.. For example this one: http://www.amazon.com/MOBILESPEC-GROUND-LOOP-ISOLATOR/dp/B001JT3I6E/ref=sr_1_22?s=automotive&ie=UTF8&qid=1356166624&sr=1-22&keywords=ground+loop+isolator" rel="nofollow - MS-205A

But you should really consider getting a quality external USB/FW soundcard as those build into laptops are in most cases just outlandisly crappy, and unless you are a big fan of Skytec (et al.), it will make your rig sound alot worse than it could with a decent input..

Edit: Till you get that isolator, taking the battery out of your laptop helps a bit too, as it reduces the load on the PSU (no battery re-charge) which makes it output less garbage.


Posted By: James Tengo
Date Posted: 22 December 2012 at 10:43am
I use http://interspaceind.com/component/virtuemart/?page=shop.product_details&flypage=vmj_ritz.tpl&product_id=32&category_id=20" rel="nofollow - these it's a di, on which you can mono sum, attenuate and ground lift the signal. Never remove a protective earth!



Posted By: b grade
Date Posted: 22 December 2012 at 4:06pm
Fair enough.  I removed my response, as I certainly would not want anyone to get electrocuted.  I have never seen that happen from an ungrounded computer, but maybe it is because we are generally wearing rubber soled shoes.

Its gotta be the shoes


Posted By: Audio_AL
Date Posted: 22 December 2012 at 4:32pm
Thanks for the help guys. This was more of a problem when im in my shop tinkering/building and I have my laptop plugged straight into my dcx. When I gig I use the soundcard on my Traktor Kontrol S4. Thanks again.

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Make it loud!


Posted By: George C
Date Posted: 22 December 2012 at 5:22pm
I found a ferrite core strapped around the mains cable to laptop removed the hum, should get one from Maplin or Tandy - anyway it worked for me!Smile 

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happiness is a ticked off list


Posted By: opus jody
Date Posted: 23 December 2012 at 4:22pm
Isn't the problem with computer buzzes the fact that they're earthed twice? through the power supply, and through the audio cable, via the mixer? and it's some slight difference in the two earth routes that causes the buzz?
If so isn't it the case that if you break the earth on the computer PSU ONLY (as you can't break the earth on the audio without also killing the audio) then it is still earthed, just through the mixer?
I appreciate that to do this involves a 'special' power cable (earth lifted) which could obviously be very dangerous in a different situation, so no-one's ever going to suggest that one should ever be built, just as sure as I am positive that no-one could possibly have one stashed away in some special place, and labeled up to fuk, for use only if 'one' happened to have a laptop on-stage that was causing his rig to buzz like a b'stard!
Big smile


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Improvised Hardware Music http://vimeo.com/user9389813/videos


Posted By: James Tengo
Date Posted: 23 December 2012 at 4:40pm
Read

http://www.jensen-transformers.com/an/generic%20seminar.pdf" rel="nofollow - http://www.jensen-transformers.com/an/generic%20seminar.pdf


Posted By: opus jody
Date Posted: 23 December 2012 at 9:19pm
Thanks Smile


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Improvised Hardware Music http://vimeo.com/user9389813/videos


Posted By: James Tengo
Date Posted: 23 December 2012 at 10:54pm
In my work as a corporate lampy (ugh... 9 years at an AV company, what was I thinking?) I was so often the first port of blame whenever the noise boys or videots experienced hum or noise (cue shouts of dirty mains, another pet hate) that a litte education session would follow, using flipcharts, of roughly the contents of that paper. Amazing how little knowledge is required to be an AV tech, and what good money you can earn with that half a clue


Posted By: b grade
Date Posted: 23 December 2012 at 11:15pm
Originally posted by James Tengo James Tengo wrote:

Read

http://www.jensen-transformers.com/an/generic%20seminar.pdf" rel="nofollow - http://www.jensen-transformers.com/an/generic%20seminar.pdf

Very interesting read for me.  It seems I must go back to some of my friends who are Ground lift happy and make them ground lift sad.  Good read and thank you for posting it.


Posted By: dlyxover
Date Posted: 24 December 2012 at 12:49am
these work a treat 

http://www.ebay.co.uk/itm/Napalm-Stereo-Isolator-Unbalanced-/260919055565" rel="nofollow - http://www.ebay.co.uk/itm/Napalm-Stereo-Isolator-Unbalanced-/260919055565


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In the Truth there is no news, and in the News there is no truth


Posted By: kevinmcdonough
Date Posted: 24 December 2012 at 8:35am
Originally posted by James Tengo James Tengo wrote:

Read

http://www.jensen-transformers.com/an/generic%20seminar.pdf" rel="nofollow - http://www.jensen-transformers.com/an/generic%20seminar.pdf


Had a quick flick through, but saved for later Smile


However yeah I'd agree, the problem I've always found in these cases is just really cheap transformer circuitry in the power block of most PC laptops, seems to introduce a huge amount of noise into the audio outs, and not just a 50hz hum sometimes quite a wide or fairly HF range of noise.

As PC laptops are all so different, its a bit of trial and error to fix it. Sometimes an external sound card is enough removed from the power supply to do it, sometimes those isolators people have linked to will work, or you can invest in a much better quality power supply/cable.

Mac's seem to be much better at this, not sure whether by design as its known they're used by lots of audio/video/media professionals or just cos the powersupplies use better electronics by default.

k


Posted By: Generalhammond
Date Posted: 24 December 2012 at 9:30am
Originally posted by James Tengo James Tengo wrote:

I use http://interspaceind.com/component/virtuemart/?page=shop.product_details&flypage=vmj_ritz.tpl&product_id=32&category_id=20" rel="nofollow - these it's a di, on which you can mono sum, attenuate and ground lift the signal. Never remove a protective earth!



+1


Posted By: dlyxover
Date Posted: 24 December 2012 at 7:59pm
I really like sowter transformers. There British too, always a bonus !

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In the Truth there is no news, and in the News there is no truth


Posted By: shagnasty
Date Posted: 26 December 2012 at 3:09pm
I have to say, I always use isolating di boxes but I haver never got rid of a hum like this on the signal side, if you 'scope the output it appears in the waveform when the psu is on, connected but not on seems fine ( negating earth (ground for those across the water) loop as cause) I am guessing a few ferries inside the smpsu would do it, or cut the DC wires and add some smoothing/decouple caps....



Posted By: wires
Date Posted: 26 December 2012 at 4:32pm
Ground loop isolator will do the trick or something like a behringer hum destroyer if you wanted. Always keep one handy just in case.



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