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Audio PA & analog switching

Discussion in 'General Electronics' started by Bernard, Jun 3, 2004.

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  1. Bernard

    Bernard Guest

    I have an audio PA which rated at 4ohms 22W in bridge tied load or
    2ohms in stereo mode. What will possibly happen to the audio PA when I
    connects a 3.2ohms speaker parallel with 16ohms speaker in bridge

    Which in my own understand that the resultant impedance is 2.7ohms can
    eventually burn the pa. Am i right?

    I am also looking for an analog cmos switch which I able to
    enable/disable the 16ohms speaker. The switch must able withstand max
    1A and 14V peak value and Ron must be ultra low <1ohms. Has anybody
    come across this component? Please tell me.

    Thank you in advance.
  2. Possibilities are higher distortion (this might endanger the tweeters)
    and increased power dissipation in the amplifier. If the amplifier is
    designed badly it may blow up. But then it probably isn't a great pity ;-)

    With an arrangement like this you can't set the volume on the two
    speakers separately. Because they're different, they may produce very
    different sound levels when driven with the same signal. Whether that
    matters or not depends on your situation, but I imagine it could be very
    A CMOS switch is not a particularly good idea for this task. Why can't
    it be a good old electromechanical relay?
  3. If the PA has some overload protection, you will get only distorted sound.
    Else it will go kaput.

    No, and likely it does not exists.
    Use a relay!

    Or, for the same price, a second amp (chip).
  4. Yeah, it's called a Relay.
  5. Guy Macon

    Guy Macon Guest

    It might survive. Maybe the designer wrote 4 Ohms minimum in the
    spec when it can actually handle 2.6 Ohms. Or maybe not.

    I can say this with confidence; the 3.2 Ohm speaker will be blaring
    and the 16 Ohm speaker will put out very low volume, and this will
    remain true no matter what amplifier you use.

    Add a 16W or larger 4 Ohm resistor in series with the 3.2 Ohm speaker
    and the volume levels will be reasonably close to each other and your
    amp will be within it's rated limits.
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