?
Solved

Headphone output on MacBook Pro has electronic noise

Posted on 2008-11-02
7
Medium Priority
?
1,664 Views
Last Modified: 2013-11-10
I have a MBP. It has a mini-plug stereo line-out/headphone jack. Headphones sound fine when plugged in. However, when I plug in a mini-plug to 1/4" Y cable in, and send that cable to my desktops external sound card (firebox), electrical noise becomes very prominent (eg. if I move the mouse, noise changes, etc). Is there a way to fix this?

sample of affected audio:
http://www.box.net/shared/yxa4cnjlx1
0
Comment
Question by:rose1013
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
7 Comments
 
LVL 31

Accepted Solution

by:
Frosty555 earned 500 total points
ID: 22864814
I'm assuming the firebox has an AC power source? If so, the problem is most likely caused by ground loop issues. Incorrect electrical wiring causes noise in audio equipment.

http://www.gbaudio.co.uk/data/ground.htm

Either find the problem (usually it is another device connected to the same fuse causing issues. so start unplugging things until you hear the noise stop).

Or, get a ground loop isolator. E.g. http://www.amazon.com/Xitel-GLI1-X1-Ground-Loop-Isolator/dp/B00023XDYA
0
 
LVL 31

Expert Comment

by:Frosty555
ID: 22864817
>>Incorrect electrical wiring causes noise in audio equipment

Okay, that's a vague, and not entirely correct statement. But more details are explained in the link below it.
0
 

Author Comment

by:rose1013
ID: 22866400
I have heard grounding issues before, and they usually don't react to changes in the computer circuitry firings, do they? I'm going to see if my college has any isolators that I could borrow to see if that does fix the problem, since 1/4" can be fairly expensive. I'll get back to you on that. Thanks.
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 31

Expert Comment

by:Frosty555
ID: 22868555
Ground loops wouldn't affect your computer. Your computer is sending the exact signal that you would expect out the sound card. But somewhere inbetween the sound card and your speakers, there is an alternative paths to ground that is causing small amount of current to flow through those wires, and that makes electrical noise on the line which you hear as an audible hum. That's what a ground loop isolator tries to prevent.

The other possibility is that the noise is coming from a device inside your computer itself. My laptop for example makes a faint "ticking" sound when I use the onboard headphone jack, because it is close to the CPU and some kind of cross-talk is occuring. But I don't think this is the case for you, because you said it works fine when you use headphones.
0
 

Author Comment

by:rose1013
ID: 22868672
At the same time, cross-talk seems more likely to me: there is a distinct change in the tone of the noise when I move the mouse, or the comp starts thinking, as I open a program, etc. The ogg i provided was this::

Idle sound
Moved mouse in the first 3rd.
Opened a program in the second third.

You can make out distinct changes in the recording. If it is crosstalk, how would I avoid that?
0
 
LVL 31

Expert Comment

by:Frosty555
ID: 22874043
If it is some kind of cross-talk or interference coming from within your computer, you could try moving around some of the PCI cards, changing position of memory, etc. But normally there is not much you can do about it. It would be a design flaw in the motherboard or in a peripheral attached to it.

That's why I'm leaning towards the ground-loop-isolator thing and hoping it solves your problem ;)
0
 

Author Comment

by:rose1013
ID: 22876026
Here's to hoping! I'll check with my tech breakout room to see about borrowing.
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I don't watch much broadcast TV directly (I hate commercials), but I do have an extensive library of video files (movies and TV episodes) on my PC's hard disk.  When I got my new Toshiba HDTV, the first thing I did was hook up the "PC Interface" as …
pc, laptop  monitor connection configurations
In this video, Percona Solution Engineer Dimitri Vanoverbeke discusses why you want to use at least three nodes in a database cluster. To discuss how Percona Consulting can help with your design and architecture needs for your database and infras…
In this video, Percona Director of Solution Engineering Jon Tobin discusses the function and features of Percona Server for MongoDB. How Percona can help Percona can help you determine if Percona Server for MongoDB is the right solution for …

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question