Amplifer Question ??

Discussion in 'General Electronics Chat' started by Dr.killjoy, Jan 7, 2015.

  1. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    I picked up a Bluetooth portable speaker and the amp board is shot ... So I am converting it to a corded speaker.. My questions is what size amp do I use cause the box has 2 4Ω 5watt speakers??? Do they have a cheap amp on ebay or am I better off building one and what a great design for my application ???




    Thanks
    Jay Sr
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Buy instead of build. Many, many inexpensive options.
     
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  3. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    What size should I look for ??? I tried looking for 5watt amps on ebay but came up with a bunch of guitar amp boxes..
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Something like this (just an example, not an endorsement, the first thing that popped up). Don't search on size, just use "audio amp" and start sifting.

    There have been specific units tested and suggested by members here. It might be worth looking for those threads as well.
     
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  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Most of these use 5 volt, high-amperage class D amplifiers powered by a 4.6 volt lithium battery.

    Usually a chip with just a few external components (two resistors, a capacitor and an inductor for each channel, if I remember correctly). More and more available in recent years.
     
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  6. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    Oh ok .. I plan on using a walwart for power and some of the orgional circuit pcb..

    I will have to do alot more searching later cause I have to clean my house right now and take care of 1yrs old daughter..
    I will have to modify my search protocol . What size amp should I be looking for ???
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    V*V/R = 5 x 5 / 4 = 6.25 watt per channel. That is at max load. You don't want to operate at max because distortion is usually really high so I would look for a 10 watt power amp for each speaker.

    However, since you want to use a pre-made DC and few are available in the 5V @ 2 amp output range, you might want to select new figures that correspond to the 7 to 10 watt AC adapter that you plan to use.
     
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  8. #12

    Expert

    Nov 30, 2010
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    A little background here. I use a 50 watt amplifier with my 100 watt speakers because the speakers retail for $800 each (20 years ago) and I want an amplifier that would be hard pressed to hurt them. You're on the other end of the spectrum where you would want good transient response and Devil take the speakers. I agree that twice as much amplifier as the speakers are rated for is the right thing to do with this job.
     
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  9. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    Ok I thinking about using using the TDA2009A chip and what do you guys think ???
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Tayda has them for $0.90 each. Worth trying. If they have too much hiss, try another solution.
     
  11. GaryCole

    New Member

    Jan 6, 2015
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    My cousin had the similar situation and he bought TDA2009A chip, he says it' ok.
     
  12. Mr.oaktree

    Member

    Dec 10, 2014
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    try parts express they have fairly cheap amplifier kits in ranges from 5watts to 1000watts , but be warned you assemble the amp . its a do it yourself kit .
    now me myself id just take the amp out of a clock radio or any audio device you have laying around the house and combine it with a nice rechargeable battery . its much more fun to give an old part new life . or you could cheap out and buy a 10$ bluetooth earpiece and gut it and upgrade the battery and install it in your speaker if more wattage was desired its very easy to use a small amp to upgrade . it all just depends on your determination and drive . do you want a quick easy project or do you wanna test your skill and have some fun :)
     
  13. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
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    Update Time

    I am going to use the TDA2009 chip and I picked up 2 8watt 4ohm speakers that are a dual cone vs the single cone 5watt 4ohm ... I was thinking about using a bluetooth chip with a rechargerable lipo cells but I don't know yet..
     
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