Phone to car stereo volume low, pre or power amp needed

Discussion in 'The Projects Forum' started by Mashly, May 6, 2016.

  1. Mashly

    Thread Starter Member

    Apr 4, 2014
    33
    1
    Hi,

    I am thinking of making something to boost the audio signal from my phone to my car stereo aux in. This is because to get any volume I have to turn the car stereo right up (even with the phone on max volume) and it introduces lots of crackles.

    I think all I need is to make a small pre-amplifier to increase the signal to the car amp, is this correct and if so can people point me to a good project that you might have done before.

    I am not sure on the voltage levels available yet but being a car there is going to be a 12V somewhere.

    Thanks,

    Matt
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    The problem is the headphone socket will have resistors on it to drop the volume, you're better getting a ready made amplifier on ebay or electronic stores.

    Adafruit do kits, but they are separate outputs for left and right, no common ground, may be better to use two separate mono amps.
    https://www.adafruit.com/search?qs=Stereo+amplifier+
     
    Last edited: May 6, 2016
  3. Mashly

    Thread Starter Member

    Apr 4, 2014
    33
    1
    Do you mean the headphone socket on the phone or into the car, as I used this hack http://www.instructables.com/id/Aux-cable-installation-for-a-Cabasse-Auditorium-6C/ to get the aux lead ion my car and I don't think there are any resistors (except maybe in the stereo)

    Surely I can make something using this http://www.farnell.com/datasheets/2002292.pdf, then connect the negative to each speaker together to create my ground and feed left and right with each speakers positive.

    The emphasis here is on making it myself to learn more about this area not just buying something :)

    Thanks,

    Matt
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    I can understand you want to learn, but a ready made kit or self assembly will be better and cheaper than making one from scratch, that chip has floating outputs and so is no good,

    try using a lm386 chip.
     
  5. Mashly

    Thread Starter Member

    Apr 4, 2014
    33
    1
    Thanks for your help, but I didn't think this site was all about telling people to give in and buy something because it is easier :( If I wanted that I would have just gone straight to adafruit/ebay/amazon.

    I would like to learn how to design good amp's. I found this http://www.instructables.com/id/The-Opa-Amp-iPod-Amp-for-Aux-In/ that originally used the LM386 but was bad sound quality and took too much power, so they used a OPA2227 so I might look into using that chip.

    Thanks anyway
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    If you want to learn.. go for it..
    PLENTY of information already out there..
    https://tangentsoft.net/audio/cmoy/

    Sometimes we get people that just want everything spoon fed to them and really have no desire to learn or do any of the work themselves..

    Give them a try and ask questions if you get stuck or want clarification...
    I too had the same issue in the past when I used the aux cables (I'm all bluetooth now) but I wanted to make my own too then just saw.. ok crap for $10-20 it all done for me.. Back in the day they were far more expensive/limited compared to the selection these days..
     
  7. Mashly

    Thread Starter Member

    Apr 4, 2014
    33
    1
    Excellent, thanks mcgyvr will have a look at the link :)
     
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