Author Topic: I think I broke my computers audio  (Read 2862 times)

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Offline wlamb02

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I think I broke my computers audio
« on: June 21, 2015, 01:59:29 am »
So i was messing around with the LM386 audio amplifier. I added an RC low pass filter (C 1000uf R 5Ohm)before the amplifier and it worked fine. Then I wanted to switch back to unfiltered audio so I put the alligator clip on the capacitor lead. The sound was crackling so I plugged in my headphones and now the right headphone has a crackling noise all the time. The computer is a MacBook Pro (13-inch, Mid 2012). Did I break something?
 

Offline wlamb02

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Re: I think I broke my computers audio
« Reply #1 on: June 21, 2015, 09:09:39 am »
bump
 

Offline Ian.M

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Re: I think I broke my computers audio
« Reply #2 on: June 21, 2015, 10:11:19 am »
The evidence suggests you have indeed broken something.  Using a motherboard or laptop audio input or output for experimenting without a very carefully designed and constructed external buffer is unwise - USB sound cards are fairly cheap and can be treated as sacrificial devices.   Changing connections with the circuit powered on and the computer audio lead connected was also unwise.  Its likely that the 1000uF capacitor had charged up somehow and when you clipped the lead to it direct, you zapped the audio output.
 

Online wraper

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Re: I think I broke my computers audio
« Reply #3 on: June 21, 2015, 10:38:38 am »
Likely you destroyed an audio codec IC if it is connected directly to the audio output or an amplifier IC if it is present on the motherboard.
 

Online wraper

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Re: I think I broke my computers audio
« Reply #4 on: June 21, 2015, 10:40:31 am »
I added an RC low pass filter (C 1000uf R 5Ohm)
Who in the sane mind uses so low R and so high C for the RC filter.
 

Offline SeanB

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Re: I think I broke my computers audio
« Reply #5 on: June 21, 2015, 10:42:49 am »
You fried an audio output chip, and if you are unlucky as well the on board multi IO chip as well, as it is connected there as well for detecting headphone insertion and line or headphone output levels. Not easy to fix, as the chip is small, and buried in the non removeable main board. Applecare might replace the motherboard if you have the extended support option, but if they do not cover it the Macbook is going to have no audio built in any more.

Solution is to buy an external USB sound device and use it ( cheap at $2 for the simplest Skype dongle with mic and headphone outputs), and use a spare one for your sound experiments.
 

Offline lewis

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Re: I think I broke my computers audio
« Reply #6 on: June 21, 2015, 10:47:34 am »
Looks like a trip to Rossmann Repair in NYC:

http://www.rossmanngroup.com/
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Offline amyk

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Re: I think I broke my computers audio
« Reply #7 on: June 21, 2015, 12:36:03 pm »
What's the model number (the one that begins with A, e.g. A1278)? Find a schematic and take a look... chances are that you blew the amp and not the DAC itself. E.g. on an A1278 the lineout amp is a MAX9724A.
 

Offline Deathwish

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Re: I think I broke my computers audio
« Reply #8 on: June 21, 2015, 12:42:41 pm »
Electrons are typically male, always looking for any hole to get into.
trying to strangle someone who talks out of their rectal cavity will fail, they can still breath.
God hates North Wales, he has put my home address on the blacklist of all couriers with instructions to divert all parcels.
 

Offline lewis

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Re: I think I broke my computers audio
« Reply #9 on: June 21, 2015, 03:48:03 pm »
Louis makes me chuckle ..

Me too, I've learned a lot from his customer relations
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Offline Alex Eisenhut

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Offline Howardlong

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Re: I think I broke my computers audio
« Reply #11 on: June 21, 2015, 04:54:06 pm »
I added an RC low pass filter (C 1000uf R 5Ohm)
Who in the sane mind uses so low R and so high C for the RC filter.

I was thinking Zobel network, but on the output, not the input, and it's also not clear how R1 comes into the equation. Even then, if that is what it's meant to be, it's a lot of C for an LM386 snubber.
 


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