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Re: Sound card question

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On 10/02/2015 10:18 PM, rlharris@oplink.net wrote:
> On Fri, October 2, 2015 5:34 pm, Doug wrote:
>>> In this context, mis-use of terms "impedance" and "power" is adding
>>> nothing but confusion.
>>
>> I have no quarrel with the advice that follows, but I do not understand
>> the comment above.
>
> Doug,
>
> As I recall, the thread began with the need to monitor the audio signal
> being fed into a transceiver from the headphone-level audio output of a
> computer.  Specifically, the question was whether a Y-adapter would
> suffice.
>
> In this application, the Y-adapter connects in parallel the input of the
> transceiver and the input of the powered speaker system.  We immediately
> get into trouble if we say "load" instead of "input", because the term
> "load" implies a transfer of power, and in this application there is no
> transfer of power from the computer output to either the transceiver or
> the speaker system.
>
> The most simple, natural, and common solution is to use an inexpensive
> (about twenty-dollars) set of powered speakers.  The term "powered
> speaker" commonly is used for an integrated unit which consists of
> speakers (left and right), amplifier(two-channel), and power supply.  The
> input (whether jack or cable with a 3.5mm stereo phone plug) of a powered
> speaker has an impedance in the range of 10,000 Ohms to 100,000 Ohms; this
> is for each channel.  Such a high impedance is all but invisible to the
> output of the computer, because the output of the computer is designed to
> pump 10 to 20 milliWatts into a pair of 8 Ohm earbuds.
>
> So we take a functional system (the computer output feeding a signal into
> a transceiver) and connect in parallel the powered speaker, which adds to
> the computer output an almost-invisible load.  And, like the powered
> speaker system, the transceiver input has a high impedance.  So,
> essentially, the computer HEADPHONE output (which has a very low
> impedance) is running unloaded.
>
> The power consumed by the speaker mechanism (which consists of voice coil,
> magnet, and paper cone) is of no concern to us, for that power is
> furnished entirely by the power supply which plugs into the 120V
> receptacle.
>
> Inasmuch as powered computer speaker systems are a commodity item (twenty
> dollars), there really is no incentive to purchase components and build
> anything.
>
> RLH
>
>
>
Ok, I think we are not fighting over anything. I did not assume speakers
as the destination when I suggested a Y adapter. _Then_ the OP said he wanted
speakers. I did not assume, as you apparently did, that he was thinking of
powered computer speakers. With the exception of some Logitech powered
speaker systems, practically all others are junk, with no attempt at
fidelity. So I would not immediately think of "computer speakers."
And yes, the input impedance of any of such systems is at least a
couple of K-ohms, and will not load the Y adapter. Another responder,
as you no doubt know, suggested an old boom-box with an external audio
input jack. That might be the simplest answer of all, if there's one kicking
around somewhere.

Cheers--doug

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Thread

Sound card question Danny <mynixmail@gmail.com> - 2015-09-30 16:00 +0200
  Re: Sound card question rlharris@oplink.net - 2015-09-30 16:40 +0200
    Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 15:50 +0200
  Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-09-30 19:50 +0200
    Re: Sound card question Seeker <seeker5528@comcast.net> - 2015-10-01 08:20 +0200
      Re: Sound card question Rob van der Putten <rob@sput.nl> - 2015-10-01 12:10 +0200
        Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 16:00 +0200
          Re: Sound card question Rob van der Putten <rob@sput.nl> - 2015-10-01 18:00 +0200
      Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 16:00 +0200
    Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-01 16:00 +0200
      Re: Sound card question rlharris@oplink.net - 2015-10-01 17:30 +0200
      Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-01 23:00 +0200
        Re: Sound card question rlharris@oplink.net - 2015-10-02 00:20 +0200
        Re: Sound card question rlharris@oplink.net - 2015-10-02 01:00 +0200
        Re: Sound card question Danny <mynixmail@gmail.com> - 2015-10-02 17:30 +0200
          Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-02 19:20 +0200
            Re: Sound card question rlharris@oplink.net - 2015-10-02 20:40 +0200
              Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-03 00:40 +0200
                Re: Sound card question rlharris@oplink.net - 2015-10-03 04:20 +0200
                Re: Sound card question Doug <dmcgarrett@optonline.net> - 2015-10-03 06:30 +0200
          RE: Sound card question "Larry Owens" <owens@netptc.net> - 2015-10-02 19:20 +0200
          Re: Sound card question David Wright <deblis@lionunicorn.co.uk> - 2015-10-02 19:30 +0200
          Re: Sound card question Stuart Longland <stuartl@longlandclan.id.au> - 2015-10-04 01:20 +0200
            Re: Sound card question rlharris@oplink.net - 2015-10-04 02:30 +0200
              Re: Sound card question Stuart Longland <stuartl@longlandclan.id.au> - 2015-10-05 23:00 +0200

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