PB-12 audio line-in problems

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adirksadirks
Posted:
in Genius Bar edited January 2014
hi Chaps,



i put it first in current hardware, but apparently it

should appear here.



working with my new 12" PB (nice!) and i cannot

get any signal from my audio line-in (from

System Preferences -> Sound -> Input). is

this a know problem or do i need to tweak

something?

i am trying to connect my headphones-mic

combination.



cheers,

adirks.

Comments

  • Reply 1 of 5
    neutrino23neutrino23 Posts: 1,575member
    How do you know it doesn't work?
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  • Reply 2 of 5
    adirksadirks Posts: 36member
    i know it doesn't work because i had connected my

    headphone-mic piece and was setting up my

    Voice over Internet phone app. and when

    i checked

    System Pref -> Sound -> Input

    for the audio line-in port i got no response,

    whereas i get a response for the

    internal mic

    it is not the headset, for i tried somebody else's

    who claims there is working.



    i went to Apple's website and there was something

    about a Hardware Check CD that should come with

    a PB 12", though i never got it (unless it is burried

    somewhere on the Software Install DVDs, couldn't find

    XCode on there either for the Developer Tools, which

    i thought should be on there).



    any suggestions how to proceed?



    thanks,

    adirks.
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  • Reply 3 of 5
    neutrino23neutrino23 Posts: 1,575member
    Does the microphone generate a line-level signal? The microphone output might be too low to be seen by the PB.



    To test the PB try connecting it to a stereo. Connect the "Rec Out" of the stereo to the sound in port of the PB. In the sound control panel with Line In selected you should be able to see some activity on the input level if it is working OK.



    If this is the problem you'll need something to boost the signal to work on the PB. One possibility is the Griffin iMic. It is a sound to USB converter. The audio input can be switched between line level and mic level.
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  • Reply 4 of 5
    adirksadirks Posts: 36member
    believe it or not, but i don't have stereo ...

    so cannot check the line-in that way.

    but i have put the Level in the Sound Preferences

    to as high as possible and get absolutely no

    response.
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  • Reply 5 of 5
    neutrino23neutrino23 Posts: 1,575member
    Just speculation but perhaps the microphone is not a line level type.



    Broadly speaking, there are two kinds of microphones, some use power (battery or external power) and have small amplifiers built in and these produce output at line level (a little less than one volt signal swing) and have low output impedance.



    Other microphones (very common) have no amplifiers or very limited amplification. These produce very low level signals (about a hundred times less than line level). They also have very high output impedance. This means that the voltage output is not able to provide much power for driving other electronics. Usually, dedicated electronics are used to amplify microphone level signals up to line level for use in other electronics.
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