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Stereo headphone combiner jack

Discussion in 'Electronic Repair' started by nil spam, Nov 6, 2003.

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  1. nil spam

    nil spam Guest

    I've got two outputs from my digital tv box and my computer both going into
    one jack which combines them into one input for my speakers. I've noticed
    something wierd in that when I plug only one of the outputs from either
    digibox/pc into the combiner and set the volume at a decent level and then
    plug in the other output, the volume of both the inputs from the speakers
    seems to diminish significantly. Conversely when I then set the output level
    of the speakers at a nice volume and then unplug one of the two inputs the
    volume increases significantly. Obviously I either have the digibox playing
    sound or the pc playing sound but never both at the same time, I just like
    to have them both plugged in so that I don't have to keep swapping the
    cables around. The combiner was a cheapo unit from Maplins (UK equivalent of
    Radio Shack) and is obviously a passive device but I never expected this to
    happen. What's going on and how can I remedy it (on a budget if possible).
    Thanks in advance!
     
  2. I do not know exactly what your arrangement is (combined into one jack
    on what device?) but it sounds as if this 'combiner' is simpy a
    Y-connector that cross connects the two input sources to the output.
    If so, it is no surprise to me that each input is partly shorting the
    other. You need either a resistive mixer, an active mixer or just a
    switch in order to avoid the problem.

    Kal
     
  3. nil spam

    nil spam Guest

    Kal,

    I don't really know what to call this thing. It has three sockets, two for
    inputs and one for output. The plug from my speakers goes into the output
    and the two plugs from the digibox and PC go into the inputs. You're right
    in saying it's basically a Y-connector. What exactly are the options you
    mention (the first two that is), and how much would I expect to pay for one?

    Thanks.

    | I do not know exactly what your arrangement is (combined into one jack
    | on what device?) but it sounds as if this 'combiner' is simpy a
    | Y-connector that cross connects the two input sources to the output.
    | If so, it is no surprise to me that each input is partly shorting the
    | other. You need either a resistive mixer, an active mixer or just a
    | switch in order to avoid the problem.
    |
    | Kal
    |
    |
    | On Thu, 6 Nov 2003 21:16:58 -0000, "nil spam" <>
    | wrote:
    |
    | >I've got two outputs from my digital tv box and my computer both going
    into
    | >one jack which combines them into one input for my speakers. I've noticed
    | >something wierd in that when I plug only one of the outputs from either
    | >digibox/pc into the combiner and set the volume at a decent level and
    then
    | >plug in the other output, the volume of both the inputs from the speakers
    | >seems to diminish significantly. Conversely when I then set the output
    level
    | >of the speakers at a nice volume and then unplug one of the two inputs
    the
    | >volume increases significantly. Obviously I either have the digibox
    playing
    | >sound or the pc playing sound but never both at the same time, I just
    like
    | >to have them both plugged in so that I don't have to keep swapping the
    | >cables around. The combiner was a cheapo unit from Maplins (UK equivalent
    of
    | >Radio Shack) and is obviously a passive device but I never expected this
    to
    | >happen. What's going on and how can I remedy it (on a budget if
    possible).
    | >Thanks in advance!
    | >
    |
     
  4. Doesn't it have a name/number on it? I am assuming that the signals
    from your digital TV box and from your computer are ordinary
    line-level analog audio. I am also assuming that you are using
    self-powered speakers. Without knowing the specifics, I will again
    assume that the powered speakers have a relatively high input
    impedance. (Does it say anything on them?)

    If so, you can make a resistive mixer by simply putting a 5-10Kohm
    resistor in series with each of the four signal leads (2 stereo
    sources). This should reduce all the levels very slightly but prevent
    them from shunting each other.

    See: http://www.wintektx.com/extras/making.htm
    Dunno offhand. See:
    http://www.jacksmusicfactory.com/default.asp?section=Mixers&group=Mini_Mixers
    or
    http://www.wintektx.com/products/PAM/

    Kal
     
  5. Josey

    Josey Guest

    Take a look at the audio switch maplin part no A94AR

    It's cream coloured, and about 2" long not green like in the photo. It's
    designed to switch the connection choosing between headset and speakers to
    one PC audio output. Might do what you want. All 3.5mm stereo jacks sockets.

    Jc.
     
  6. 5-10K for _speaker-level_ stuff? That's not going to work well, not at
    all...
     
  7. The one reply here that mentions a switch would seem to be your best bet.
    Using resistors to connect both outputs is going to cause you signal loss, to
    probably an unaccepable degree.

    Note that by combining both sets of outputs in a direct fashion this way you
    are risking damage to either or both of them!
     
  8. Please note that the suggestion was based on the assumption that the
    speakers were self-powered and, therefore, their inputs were high
    impedance line-level signals. 5-10K will work fine there.

    Kal
     
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