Guidance needed in building an amplifier

Discussion in 'The Projects Forum' started by justinblain, Jun 13, 2014.

  1. justinblain

    Thread Starter New Member

    Jun 13, 2014

    I had an old stereo and it had stopped working so i have removed it's speakers.
    Now i want this speakers to be used with mobile/laptop/portable mp3 players.

    Basically i don't belong to the field of electronics so i have no knowledge about circuits and electronic components. so i need complete guidance about building a amplifier for my speakers. and ofcourse i have tried finding amplifier in electronic shops but they don't have any amplifier which suit my speakers.

    I have attached snap of the speakers for details of speakers' output.

    Now for power supply i have my old phones' chargers
    one provides output of 5V 0.7A
    and other with 5V 0.89A

    I dont know if any of the chargers can be used to provide input for amplification but if any of them can be used then kindly guide me about the things i will need along with diagram to build an amplifier.
    if it needs more power supply then let me know how much power will it need..

    thanks in advance..
  2. MrChips


    Oct 2, 2009
  3. justinblain

    Thread Starter New Member

    Jun 13, 2014
    Thanks for the reply
    And ya i found such boards as a solution when i googled but it provides output of 3W per channel and i think my speakers can produce 4.5W output so i will not be able to use the max power of speakers.
    That's why i want to build one that perfectly suits my speakers.
  4. PatM

    Well-Known Member

    Dec 31, 2010
    Nominal output is 2.8W
    The MAX is 4.5W
    Loud peaks should not exceed the 4.5W
    Stay with the 3W so you do not exceed the 4.5W MAX
    You should be more worried about having a amplifier that will match 4 ohm speakers and not use one designed for 8 ohm or 16 ohm speakers.
  5. MrChips


    Oct 2, 2009
  6. BobTPH

    Senior Member

    Jun 5, 2013
    Well, the two power adapters you mentioned put out 3.5W and 4.5W total, so neither of them would be able to put out 4.5W to each of two speakers.

    The 3+3W amp linked to by MrChips is probably the best you are going to do.

    And by the way, the difference between 3W and 4.5W is barely audible. It takes about 10X the power to sound twice as loud.

  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    His power source (the best one he had) is "5V 0.89A" which can deliver a total power of 4.45W, and with an amp efficiency of maybe 70% that will be 3.11W total output or 1.55W per speaker.

    MrChips gave the best option, that little digital amp (class D) chip will give the best output power into those speakers from a 5v 0.89A PSU. It will run close to 90% efficiency and give maybe 2W per speaker actual output power. That's pretty loud!
  8. justinblain

    Thread Starter New Member

    Jun 13, 2014
    If this is the case then i'll go for the Class D amp.

    Thank you everyone for the helping me out.. :)
  9. Merlin3189

    New Member

    Oct 20, 2013
    Just a thought.
    I wonder why the stereo stopped working?
    If it was the amp, then why not put a new amp in and use the existing power supply?
    If it was the PSU then get a new PSU for the existing amp.
    I don't know your objective here, but if you were happy before it stopped, then taking out the speakers and building everything else including a new enclosure seems like making work. Of the four main things you need, power, amp, speakers and enclosure, probably only one needs replacing. Although if the amp is ok, you'll still need to add a USB interface/preamp and the enclosure needs an extra socket for the USB input.
  10. justinblain

    Thread Starter New Member

    Jun 13, 2014
    Actually that stereo plays audio cassettes and radio.. It stopped working few years back so i got it repaired but it did not work long and stopped working again and nowadays no one uses audio cassettes and even it is not playing my old audio cassettes properly but the sound quality of the speakers is so good that i don't want to just throw it away.. And i m not having much work nowadays so it will be a good pass time too..