A few Earphone/Headphone jack questions...???

Discussion in 'Computer Support' started by BIG DAVE, Dec 28, 2010.

  1. BIG DAVE

    BIG DAVE Guest

    Is a Earphone/Headphone jack the same as an EXTERNAL SPEAKER jack? On
    a PC, it SEEMS that they are one and the same however on any stereo or
    radio I have if I hook up a small speaker through the earphone/
    headphone jack the sound coming from the speaker is very low.

    I know that there are things such as matching impedence etc... But
    even after trying several speakers, the output seems low. Problem
    is... if it's NOT the same it seems that most music players or even
    radios these days don't have external speaker jacks and just have the
    headphone jack.

    Thanks

    DAVE
     
    BIG DAVE, Dec 28, 2010
    #1
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  2. BIG DAVE

    richard Guest

    On Tue, 28 Dec 2010 13:42:20 -0800 (PST), BIG DAVE wrote:

    > Is a Earphone/Headphone jack the same as an EXTERNAL SPEAKER jack? On
    > a PC, it SEEMS that they are one and the same however on any stereo or
    > radio I have if I hook up a small speaker through the earphone/
    > headphone jack the sound coming from the speaker is very low.
    >
    > I know that there are things such as matching impedence etc... But
    > even after trying several speakers, the output seems low. Problem
    > is... if it's NOT the same it seems that most music players or even
    > radios these days don't have external speaker jacks and just have the
    > headphone jack.
    >
    > Thanks
    >
    > DAVE


    Yes, the jacks are different. Headphones generally have a higher impedance
    than standard speakers, which are typically set at 8 ohms.
    If the output appears to be low, then you might have to add a small preamp
    inline.
     
    richard, Dec 29, 2010
    #2
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  3. BIG DAVE

    PeeCee Guest

    On 29/12/2010 10:42 a.m., BIG DAVE wrote:
    > Is a Earphone/Headphone jack the same as an EXTERNAL SPEAKER jack? On
    > a PC, it SEEMS that they are one and the same however on any stereo or
    > radio I have if I hook up a small speaker through the earphone/
    > headphone jack the sound coming from the speaker is very low.
    >
    > I know that there are things such as matching impedence etc... But
    > even after trying several speakers, the output seems low. Problem
    > is... if it's NOT the same it seems that most music players or even
    > radios these days don't have external speaker jacks and just have the
    > headphone jack.
    >
    > Thanks
    >
    > DAVE



    Dave


    The output level from an External Speaker jack hand depends very much on
    the design of the particular hardware and what it is intended to drive.
    If the device is designed to drive bare unamplified speakers then the
    output level will depend on the size of the power amplifiers built into
    the device. eg 500Watt Surround sound Amplifier, TV, Radio etc...
    The physical size of the speakers needed is irrelevant.
    However parameters like power handling, frequency response, impedance
    are relevant in that they should match the device they are plugged into.

    Typical speaker parameters are in the lower impedance range eg. 4 to 8
    ohms (exceptions of course, like the old Philips Hi Impedance range)

    The output level from a 'headphone' jack on the otherhand is limited by
    design to minimise potential hearing and hardware damage.
    (headphone includes earphone in this context)
    A lot of countries have health and safety limits on the maximum sound
    level a headphone can deliver to the wearers ears.
    To meet these legislative and physical constraints circuit elements are
    introduced between Amplifier and the headphone socket so it doesn't blow
    the headphones or the wearers ears up.
    (roughly <100 milli watts 'maximum')
    Note this is 'Even if the amplifier is capable of hundreds of watts
    output to speakers'

    Typicaly headphones today also tend to have higher impedances, eg up to
    32 ohms impedance.

    Therefore when you plug a low impedance speaker into a high impedance
    (headphone) output the speaker is:
    (a) not matched correctly for maximum power transfer 'and'
    (b) the headphone circuitry simply can't deliver the 'amount' of power
    to drive the speaker hard enough to hear it without close coupling to
    your ear (as in headphones)
    *this is why your speaker experiments sounded so quiet*



    FYI PC sound cards were originally designed to drive plain 'unamplified'
    speakers (think the original Soundblaster cards)
    Plugging a set of headphones into those outputs required you to turn the
    sound level 'wayyyyy' down if you valued you hearing and/or headphones.

    Later on the sound card makers transfered these Amplifiers from the
    Sound Card to the external speakers that were plugged into these new
    design cards.
    The point in the circuitry they put the output socket was roughly
    equivalent to the power and impedance of a headphone socket.
    Hence the 'Speaker/Headphone' designation.

    So a pair of (amplified) PC speakers can be plugged into a PC sound card
    'speaker/headphone' socket and sound just as loud as the old onboard
    amps to a plain unamplified speakers.

    The same amplified PC speakers plugged into the 'headphone' socket of a
    DVD player, Radio, TV etc would also give similar volume as the driving
    device is matched correctly to the (amplified) speakers.
    The power to drive the speakers loud enough to hear across the room
    comes from the speakers built in amplifiers not from the output of the
    headphone socket.

    Best
    Paul.
     
    PeeCee, Dec 29, 2010
    #3
  4. BIG DAVE

    BIG DAVE Guest

    Thanks for the replies. Paul, I especially found your reply both
    thorough and informative.

    DAVE
     
    BIG DAVE, Dec 29, 2010
    #4
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