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Pot Recomendation for Audio Amp Input

Discussion in 'Electronic Design' started by Ben Hartley, Mar 13, 2013.

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  1. Ben Hartley

    Ben Hartley Guest

    I am connecting the input of a TDA2040 audio amp to the line out of my
    laptop computer. I would like a volume control (voltage divider) on
    the TDA2040 PCB itself, instead of adjusting it on the laptop. What
    value pot should I use, assuming the laptop is set to maximum possible
    output level.

    This is the amp circuit I intend to use:

    Should it be log or linear?

    Ben Hartley
  2. Phil Allison

    Phil Allison Guest

    "Ben Hartley"

    ** 10kohms, audio type or log.

    Labelled " 10KA " or maybe " 10KC " .

    Piece of cake.

    .... Phil
  3. Phil Allison

    Phil Allison Guest

    "Rheilly Phoull"

    ** With a load of 22kohms ?

    That is not ideal.

    .... Phil
  4. miso

    miso Guest

    I think the polarity of C7 is backwards.

    A line output on a soundcard these days is pretty beefy since they often
    drive earbuds. The impedance should be about 100 ohms. Your load is 22K
    at audio frequencies. I'd make the pot 1k to maybe a 4.7K. Log.

    Depending on what you are trying to achieve, I'd consider an amplifier
    with a bridged output. That would get rid of the electrolytic in the
    output between the chip and the speaker. TI/National makes the for flat
    panel TVs. The chips are a bit more modern than the old car stereo stuff.

    Those designs with large coupling caps in the output often "thunk" on
    power up.
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