Help with audio amplifier

Discussion in 'Electronic Basics' started by Brian, May 6, 2004.

  1. Brian

    Brian Guest

    I bought a Radio Shack mini amplifier (277-1008) to learn about what makes
    them tick. Mainly because it's such a simply amplifier. I've written down
    all the components and was about to order a duplicate set to build an amp
    from scratch, but wanted to ask a quick question before I did that.

    When I turn the amp on, there's always an amount of static. What are some
    ways to improve the sound quality? The amp IC that it uses is the 386D:

    http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=
    224207

    Thanks for any help!
    Brian, May 6, 2004
    #1
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  2. > When I turn the amp on, there's always an amount of static. What are some
    > ways to improve the sound quality? The amp IC that it uses is the 386D:


    If that's the little handheld amplifier I think it is, I've tinkered with it
    a few times...

    1) That static you hear when you turn on the unit is likely due to a dirty
    volume pot. Dust gets inside it and causes this.

    2) The "386D" is just a plain old LM386 audio amplifier. These are very
    plentiful. It can be configured in a variety of ways to get more or less
    gain.

    3) The only downside to this little amp is, the tiny speaker doesn't offer
    much bandwidth. It has practically no bass at all. There's also no power
    indicator, and I added an LED so I wouldn't accidentally leave the amp on
    and drain the battery.

    Matt J. McCullar, KJ5BA
    Arlington, TX
    Matt J. McCullar, May 6, 2004
    #2
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  3. Brian

    Brian Guest

    Thanks for the help, Matt. I noticed that the traces were terribly dirty
    and scraped up when I opened it up. If I continue to hear static, is
    there anything else you would suggest to diagnose what is wrong?



    "Matt J. McCullar" <> wrote in
    news:WGgmc.14705$:

    >
    >> When I turn the amp on, there's always an amount of static. What are
    >> some ways to improve the sound quality? The amp IC that it uses is
    >> the 386D:

    >
    > If that's the little handheld amplifier I think it is, I've tinkered
    > with it a few times...
    >
    > 1) That static you hear when you turn on the unit is likely due to a
    > dirty volume pot. Dust gets inside it and causes this.
    >
    > 2) The "386D" is just a plain old LM386 audio amplifier. These are
    > very plentiful. It can be configured in a variety of ways to get more
    > or less gain.
    >
    > 3) The only downside to this little amp is, the tiny speaker doesn't
    > offer much bandwidth. It has practically no bass at all. There's
    > also no power indicator, and I added an LED so I wouldn't accidentally
    > leave the amp on and drain the battery.
    >
    > Matt J. McCullar, KJ5BA
    > Arlington, TX
    >
    >
    >
    >
    Brian, May 6, 2004
    #3
  4. The LM-386 is considered rather noisy by many... since it's audio
    bandwidth is full range. You can add some tone controls to the circuit
    that will tame down the hf noise and hiss you hear.

    Radio Shack used to sell a neat pc board kit for the LM-386, which showed
    the frequency responce and how specific parts would modify the frequency
    response. If you were really serious about working with the 386, I can
    scan and Email you a copy. Drop me a note through the radiowrench web
    page if you want to reach me.

    cheers

    skipp

    www.radiowrench.com


    : Brian <> wrote:
    : I bought a Radio Shack mini amplifier (277-1008) to learn about what makes
    : them tick. Mainly because it's such a simply amplifier. I've written down
    : all the components and was about to order a duplicate set to build an amp
    : from scratch, but wanted to ask a quick question before I did that.

    : When I turn the amp on, there's always an amount of static. What are some
    : ways to improve the sound quality? The amp IC that it uses is the 386D:

    : http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=
    : 224207

    : Thanks for any help!
    Skipp is from radiowrench dot com, May 7, 2004
    #4
  5. Brian

    Brian Guest

    Skipp, sent you an email a couple of days ago to the nospam4me address on
    your website. It was the only one I could find.


    Skipp is from radiowrench dot com <> wrote in
    news:c7eho5$g0d$:

    > The LM-386 is considered rather noisy by many... since it's audio
    > bandwidth is full range. You can add some tone controls to the circuit
    > that will tame down the hf noise and hiss you hear.
    >
    > Radio Shack used to sell a neat pc board kit for the LM-386, which
    > showed the frequency responce and how specific parts would modify the
    > frequency response. If you were really serious about working with the
    > 386, I can scan and Email you a copy. Drop me a note through the
    > radiowrench web page if you want to reach me.
    >
    > cheers
    >
    > skipp
    >
    > www.radiowrench.com
    Brian, May 8, 2004
    #5
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