Boosting the signal output from a MP3 player

Discussion in 'The Projects Forum' started by Otaku, Oct 19, 2012.

  1. Otaku

    Thread Starter Active Member

    Nov 19, 2008
    128
    2
    Hi all,
    I'm trying to find a simple transistor amplifier circuit that can boost the signal from a MP3 player from the typical 0.5 - 1.0mV range up to a value that can drive a transistor switch (~1V). For simplicity's sake, I'd like to avoid using op-amp IC's, if possible. The very low voltage from the player can't pull up the base on the 2N2222 that I'm using for the switch. All advice is appreciated!

    Gary
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    I don't know where you got the spec of 1 mV for an MP3 player output? The ones I have that drive headphones put out way more than that, probably more like 500mV signal at 0 dB.

    And what are you expecting the amplifier stage to drive?

    What signal level do you need it to put out?
     
  3. Otaku

    Thread Starter Active Member

    Nov 19, 2008
    128
    2
    Thanks for the reply, bountyhunter. I re-checked the mV values for my player and get 10-12mV DC, and ~250mV AC when it's playing a sound file (had the wrong scale set on the DMM). What I need to do is boost this voltage high enough to turn on a 2N2222 transistor, I'm assuming >/= 0.7VDC. I want to use the 2N2222 to switch 5VDC to a small DC motor.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    I don't know what you are trying to do. Turn on a motor anytime there is audio present? If so, this is really the wrong way to do it.
     
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