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Reduce sensitivity of 100K ohm volume potentiometer?

Discussion in 'Electronic Basics' started by [email protected], Nov 13, 2012.

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  1. Guest

    I have an audio DSP filter for my amateur radio equipment. It uses an LM380op-amp in the final AF amp stage, using a 100K ohm pot as the volume control. When using a speaker the volume control is fine, but when using headphones, the sensitivity from quiet to really loud is only a small tweak of thevolume know.

    Anything I can do to reduce this sensitivity for my headphone output?

    Larry
     
  2. Jamie

    Jamie Guest

    Have you thought about using a resistor?

    Just a thought really.

    You could also use a rheostat voltage divider so you
    can make adjustments to the range of the divided output for
    head phones to match the speaker, but I would go for the
    R..


    Jamie
     
  3. It's always been pretty common to put a resistor between an audio
    amplifier and any headphones. First, it puts a limit on how much can feed
    into the headphones (which may not be able to handle as much as a speaker)
    but it also acts as an attenuator with the impedance of the headphones.
    IN the tube days, this meant that you wouldn't need to keep the volume
    control low, where hum generated by the filament in the output amplifier
    could dwarf the signal. If the signal is attenuated after the
    amplification, you need to turn up the volume which then makes the wanted
    signal larger in reference to the hum. This attenuator on the output
    would also cause you to raise your volume control, making it work more
    like it would with a speaker.


    Michael
     
  4. amdx

    amdx Guest

    I'm with the Jamie and Michael, Put a series resistor in the
    headphone path.
    Another option put a 10k potentiometer in series with the 100k
    and use the 10k as a fine tune adjustment of volume.
    Mikek
     
  5. Les Cargill

    Les Cargill Guest

    http://www.electronics-tutorials.ws/attenuators/attenuator.html
     
  6. Phil Allison

    Phil Allison Guest

    I have an audio DSP filter for my amateur radio equipment. It uses an LM380
    op-amp in the final AF amp stage, using a 100K ohm pot as the volume
    control. When using a speaker the volume control is fine, but when using
    headphones, the sensitivity from quiet to really loud is only a small tweak
    of the volume know.

    Anything I can do to reduce this sensitivity for my headphone output?

    ** There needs to be a resistor of about 150 ohms in series with the
    headphone jack, this allows for phones of 8 ohms rating through to 600 ohms
    to be used without much change in volume.

    The volume pot needs to be a " log" or " audio" taper - usually marked
    with the letters "C" or "A" after the value in ohms.

    Pots marked with a "B" are linear types.


    .... Phil
     
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