Video killed my audio stars

February 16, 2009 4:43 PM

Plugging in an external monitor to my Macbook Pro kills the audio. What's up with that? And is there a solution that does not involve an expensive USB audio product?

My Macbook Pro is attached to a stereo system, which has worked just fine and dandy...until I plugged in a DVI cable and suddenly the audio was almost overwhelmed by static and "machine noise" (e.g., there are changes in the sound when I press keys or scroll windows). I usually associate this with poor shielding on cheap sound cards...what's up with my Macbook?

More importantly, is there anything I can do to fix this? I'd really like to be able to use an external monitor. One solution is some sort of external USB-connected audio device, but I'm not entirely sure what my options are...the only things I've found are (a) headphones, when what I really want is 1/8" stereo out, or (b) audio input devices like the M-Audio FastTrack (which also support audio out). I don't want just headphones, and I don't need anything as fancy as the USB connected devices I've found.

Thanks for your suggestions!

posted by larsks to computers & internet (9 comments total)

Are you certain the monitor doesn't have an audio output of its own? If so, channel the sound through that way.

This is super cheap, although I can't vouch for its quality.

Finally, these guys will definitely have an answer if someone here doesn't.
posted by fantasticninety at 4:48 PM on February 16

Have you tried calling Apple? Sounds like a hardware defect.
posted by wongcorgi at 5:13 PM on February 16

Also, if its out of warranty, you can pick up USB sound output devices for around $10 on newegg. I have a bunch that I keep around, and they dont require drivers for OS X or windows.

http://www.newegg.com/Product/Product.aspx?Item=N82E16812186046
posted by wongcorgi at 5:16 PM on February 16

When this happens, what do you see in the output tab of the Sound preference pane (Apple Menu->System Preferences->Sound)? The solution to your problem may be as simple as selecting the correct output (in my system, it's called "Internal Speakers|Built-in Audio"). OS X should remember this preference next time you plug in the monitor.
posted by strangecargo at 5:44 PM on February 16

Are you plugging both your laptop and monitor into grounded outlets? Are they properly grounded? Do they share the same ground?

What happens, if anything, to the distortion when you unplug your laptop from power but still have sound playing and the monitor attached?
posted by odinsdream at 6:26 PM on February 16

odinsdream: the noise is independent of whether the computer is plugged in or not. I'm reasonably certain this isn't a grounding-loop sort of problem; the noise isn't the sort of hum I would expect from that.

strangecargo: It's already using the correct output. That's why it's been working for all these months!

fantasticninety and wongcorgi: Thanks for the product suggestions!
posted by larsks at 6:56 PM on February 16

FWIW, I use the iMic with my iMac and it works really well. Never a problem. It even sounds great when I record old tapes and records through it's input.
posted by thebigdeadwaltz at 7:50 PM on February 16

If I understand your setup, you should be able to solve this problem for about three bucks.

My Macbook Pro is attached to a stereo system…How? Are you plugging the stereo into to audio out port (headphone port) of the Mac using mini RCA jacks and a splitter cable to separate the left and right channels?

If so, help is two millimeters away. That same audio out port on the Mac is a "Combined optical digital output/analog line out (minijack)" port. What you're getting now is analog audio. But buried slightly deeper in that port (so the minijack won't damage it) is a Toslink digital fiber optic jack. Just buy the proper adapter, and connect your stereo via the digital output. (Hope your stereo has digital fiber optic input).
posted by dinger at 4:47 AM on February 17

I second "hardware defect." I've had many Apple laptops and never had this problem. (And I routinely plug in an external monitor while listening to audio through an external speaker system.)
posted by raf at 5:38 AM on February 17