phone boombox amp

Discussion in 'General Electronics Chat' started by lokeycmos, Feb 27, 2011.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    Ok, i have done some research on this before i posted. there have been others that want to build an amplifier for ipod, phones, etc. i want to do something similar but more complex. there are thousands of amplifier circuits on the internet. ill tell you want im looking for and hoping i can get some help from the experts!

    -input: cell phone, ipod, mp3 player.

    -stereo in/out

    -preferebly runs on a 12 sla battery but not necessary.

    -volume, bass and treble controls(bass boost is a plus)

    -simple as possible without sacrificing quality

    i dont know how many watts i need, but would like it to shake the floor at full bass/volume(depends on the speakers i pick out)

    thank you all very much!

    im not sure what speaker impedance im using yet
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    You will not shake the floors with an amplifier powered from only 12V.
    You need an amplifier with an output of at least 50W RMS per channel for at least 2 channels. The speakers need to be big enough to produce bass frequencies. The speakers do not produce the power, the amplifier produces the power.

    If a speaker is 8 ohms then a single-ended amplifier powered from 12VDC drives it with about only 1.5W. A 4 ohm speaker gets only 2.7W. A bridged amplifier driving a 4 ohm speaker produces about 10W.

    Use a power supply of 62V to power a single ended amplifier that will produce 50W into an 8 ohm speaker.

    Why do you want to use a battery?
     
  3. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
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    the battery is for portability, but not necesary. ill just use mains. can you recommend a circuit that is close to what im looking for? ty
     
  4. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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  5. Audioguru

    New Member

    Dec 20, 2007
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    The datasheets tell you the output power:
    1) The TDA2050 produces 32W into 4 ohms or 18W into 8 ohms. Most home speakers are 8 ohms so it will not be loud enough.
    2) The LM1875 does not have enough power since its output is only 20W into 4 ohms or 8 ohms.
    3) The TDA1554 also does not have enough power since it produces only 10W into 4 ohms for each of its two channels.

    An LM3886 produces 50W into 8 ohms with very low distortion.
    Tone controls are part of a preamp circuit that you need to drive the power amp.
     
  6. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    Thank You! the lm3886 is a very simple circuit! now i just have to find a suitable preamp circuit.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    Here is a website with many good audio projects including bass and treble tone controls etc.: http://www.sound.westhost.com/index2.html
     
  8. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
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    im looking into the lm3886. have a question. on the datasheet @ http://www.national.com/ds/LM/LM3886.pdf im trying to figure out the Rm value on pin 8. on page 8 is a formula for the value. im lost, could someone please offer some advice?
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    Pin 8 must be -2.6V from the output DC voltage with a current of 0.5mA for the IC to mute. It is fed from the negative supply so the formula for Rm is (-VEE minus 2.6V) divided by 0.5mA.
     
  10. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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  11. Audioguru

    New Member

    Dec 20, 2007
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    The second circuit is designed by idiots because it is missing the important parts recommended by the manufacturer.
     
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