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  • external speaker

    Hi, maybe a dumb question, but if I hook up an external speaker (8 ohm) to the speaker outputs of one of the picaso display modules, wouldn't I be effectively putting 4 ohms on the output of the driver? Unless, I disconnect the onboard speaker?

    I'd like to hook up a slightly larger speaker to the module but didn't want to supply my own amplifier, unless there's an easy way to do that...

  • #2


    Hi Capricornone,

    wouldn't I be effectively putting 4 ohms on the output of the driver? Unless, I disconnect the onboard speaker?

    :: Yes. The addition of another 8 ohm speaker in parallel will result to a 4 ohm output load. In this regard, it is also best to consider requirement of the chip driving the audio, that is- to have a minimum of 8 ohms as output impedance. (reference: TPA6205A1 audio power amplifier).

    I'd like to hook up a slightly larger speaker to the module but didn't want to supply my own amplifier, unless there's an easy way to do that...
    ::I'm afraid that there are no other ways around it. Hooking up a new speaker (without any amplifier) will produce a sound a little louder than the built-in speaker but it does not add to the output power of the audio driving chip (TPA6205A1). This means that if you would require a louder output sound then using an audio amplifier would be the only way.

    Best Regards,
    Bryan

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    • #3


      Ah, this makes sense.

      So, next question. I noticed the Audio Output pin is outputting a filtered analog line level signal, is there a simple amplifier that can be built using this output? Is there a reason for this kind of output instead of the raw PWM signal, which would be easier to amplify with a Class D amplifier circuit?

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      • #4


        mm...okay, did a little more research on amplifiers, I don't think a Class D would be much simpler, was just hoping to be able to drive the speaker with a single transistor, but I don't think that's possible.

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        • #5


          Hi Capricornone,

          Reading through your recent post, sadly it is not possible to get the raw PWM. Also, the output signal on the audio I/O pin on the 30 way header is filtered beforehand. This filtering makes the signal an analog rather than a raw PWM.

          The most practical and feasible solution would be to have the output signal fed to an external amplifier to attain the objective of putting up the sound. A simple USB powered amplifier will surely do the trick. Also, simply using an external amplifier will greatly reduce the possibility of damaging the device.


          Best Regards,

          Bryan

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          • #6


            Hello
            with uLCD43PTC, where (pin) i can connect an (instead of internal) with 8 ohm and watt ?

            Thanks in advance

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            • #7


              You will need to remove the internal speaker and connect your external one to the same pads. The speaker should be 8ohms of at least 1.25 watts.

              Note that the -ve speaker terminal is not GND.
              Mark

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