Tips For Installing A Headphone Jack

Discussion in 'General Electronics' started by Larry G., Aug 17, 2003.

  1. Larry G.

    Larry G. Guest

    I just purchased a new Apex stereo TV/DVD combo with many bells &
    whistles EXCEPT a headphone jack. Have any of you readers been able
    to successfully install a stereo headphone jack into a stereo TV?
    Thanks.
     
    Larry G., Aug 17, 2003
    #1
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  2. Larry G.

    Rich Grise Guest

    (Larry G.) wrote in message news:<>...
    > I just purchased a new Apex stereo TV/DVD combo with many bells &
    > whistles EXCEPT a headphone jack. Have any of you readers been able
    > to successfully install a stereo headphone jack into a stereo TV?
    > Thanks.


    Yes, I have. One thing to watch out for is that both of the speakers'
    "ground" or "return" lines are common, i.e., electrically the same
    point. I forget what the jack is called, but it's got 5 terminals:
    The sleeve, obviously, which is the speaker common. Then it has two
    contacts which contact tip and ring, but they get their signals from
    the other contacts. When you push the plug in, it disconnects the
    speakers and goes to the phones.


    audio out o-------------------------\/
    ^
    | <<<---- plug
    o----------------+
    |
    |
    +---------------------------------> to speaker


    When you plug in the plug, it opens the contact. There are two of
    these circuits in the jack.

    Good Luck!
    Rich
     
    Rich Grise, Aug 19, 2003
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  3. Larry G.

    skipper

    Joined:
    Jun 24, 2009
    Messages:
    1
    The simplest approach is to wire the headphone jack to the speaker outputs through an attenuating circuit. The things to be careful though is that the output amp circuit needs to be properly loaded in order to provide the correct audio response and to protect both the amp circuit and headphones from over-currents. The impedance expected by the amp and that expected by the headphones need to be accounted for to flatten the frequency response and minimize distortion and noise. Finally, it doesn't take much to drive headphones to painful levels:

    WARNING
    Headphones are rated in dB SPL at 1mW, and this circuit is capable of producing extreme SPLs. The levels obtainable are sufficient to cause almost instantaneous permanent hearing damage! Never operate the player at very high levels, and never switch the amplifier on with signal while wearing your headphones.

    Always start with the volume control at minimum, and gradually increase the level until it is comfortable, but not too loud. Because of the very low distortion, it is easy to increase the level too far without noticing. Your ears are precious - safeguard them at all times.


    That said, here is an article to calculate exactly what you need:
    sound.westhost.com/project100.htm
    and I attached it's circuit diagram:

    sound.westhost.com/p100-f1.png

    Here is a limiting circuit that you can wire between the above resisters
    and the jack itself to protect your ears:
    wa0itp.com/audiolimiter.pdf
     
    skipper, Jun 24, 2009
    #3
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