MP3 Player Amplifier

Discussion in 'General Electronics Chat' started by tracecom, Jul 16, 2010.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    When I connect the output from my MP3 player to the auxiliary input of my car radio, the volume is significantly lower than the other sources (tuner, CD). Thus, when I adjust the volume for the MP3 player and then stop it, the volume for the tuner is startlingly loud.

    Does anyone have a simple stereo amplifier circuit that I could build to remedy this situation? It doesn't need to be high gain, but I would like it to be stereo and powered by the nearby USB output.

    Thanks in advance.
     
  2. BMorse

    Senior Member

    Sep 26, 2009
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    I pretty much have the same issue...

    Have you tried adjusting the volume on the MP3 player when plugged into the auxiliary port on the stereo? I usually have to do that when I connect my mp3 player to my truck stereo (But the volume difference for the tuner/CD is still very loud when I switch to that without turning the volume down first), and I also noticed that as the charge in the MP3 players battery gets used up the volume also goes lower.... so the output strength of the player is proportional to the battery power level apparently...

    B. Morse
     
  3. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    Yes, if I turn the volume on the MP3 player wide open, it helps, but still not enough.

    That may also be the case, but I haven't really noticed it. My concern is that turning the MP3 player volume wide open will drain the battery faster.

    It seems that a low gain amp should be fairly easy to build. If it was powered off the USB port, there would be no batteries to worry with, and I would likely power the MP3 player off the USB as well.

    It seems like a product Belkin or someone would come up with.

    On a related note, I have the same issue when I plug a flash drive into the USB port: low volume there too. Makes me wonder what the designers of the car radio were thinking.
     
  4. BMorse

    Senior Member

    Sep 26, 2009
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    The small amplifier could work, but I may have to power it off of the stereo power, possibly using the remote turn on output to turn it off and on with the stereo, since I do not have the USB port available on my receiver (But I do have several available from my carputer, but then I would have to have that on to power the MP3 player, which if I had the carputer on, I wouldn't need the mp3 player at all! The dilemma's of modern technology I guess ;) )......

    What if you had a pair of portable self powered speakers for the MP3 player (Which quite a few can be bought at Wall Mart for cheap, or other similar stores), and hack that to use the amplifier circuit in that... I am sure the circuit board is probably pretty small, and they usually run off of 4 AA's, so powering that from a 5 volt USB port shouldn't be an issue, or even a 5 volt regulator plugged into the cigarette lighter/aux power port... I think I will have to check into this, could make this a simple solution for both our problems without too much hassle!

    B. Morse
     
    Last edited: Jul 16, 2010
  5. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    That would work, and I have an old set of stereo computer speakers with an amp that I would be willing to sacrifice. The gain would be way too high, but there is a potentiometer control that I could adjust to match the volume. The amp runs off a wall wart, and I don't remember the output voltage. I'll dig through the junk and see if I can find the speaker set.

    Not the most elegant solution, but probably the cheapest in the long run.
     
  6. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    Found the speakers and the wall wart is 9 volt output, so it's possible that, given the low gain I need, a 9 volt battery might provide sufficient capacity.

    ETA: Attached is the photo of the amp PCB; it's definitely overkill for what I need.

    Surely someone has a simple circuit to do this.

    [​IMG]
     
    Last edited: Jul 16, 2010
  7. flat5

    Active Member

    Nov 13, 2008
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    I would try two step up audio transformers.
    This sounds like an impedance issue to me.
    They would be very small and require no power.
    Digikey or someplace like it would have the parts you need. I'm guessing 32 ohms to something over 500 ohms will do.
     
  8. vindicate

    Active Member

    Jul 9, 2009
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  9. BMorse

    Senior Member

    Sep 26, 2009
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    Yeah, I could make my own pre-amplifier circuit, PCB, etc.... but where is the fun in that? I actually already have a few modules built around the LM386 amplifier, such as this one:

    [​IMG]

    But, sometimes, "hacking" is a little more fun....

    Well, since I am just going to make my own, might as well incorporate a 5 volt power source for USB devices like my MP3 player, that way, I can charge and listen at the same time while in my truck, then I will not have to worry about the sound fluctuating with the battery level....

    B. Morse
     
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