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LM386 Amplifier Project

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by TheNewGuy, Aug 25, 2009.

  1. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The parts go on the side without copper. The connecting wires are soldered to the parts' wires on the copper side.

    The quality of the RadioShack board is poor because the copper is too thin, its glue does not hold and the holes are too big so be careful when soldering to it.
     
  2. TheNewGuy

    TheNewGuy Member

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    I found this video

    So I did it, with out any board or anything, because I screwed the entire thing earlier with that complicated schematic I drew.

    The only thing I did differently was that the wire I used was copper wire.

    The sound quality was a million times worse than what it is in that video. It was horrible!

    Pin 2 was connected to Pin 4, pin 4 was connected to negative terminal of 9V battery. Pin 5 was connected to a 10uF Capacitor which was connected to positive of a cmos speaker out of a computer. Pin 6 was connected to positive.

    Pin 3 (input) was connected by an auxjack to my phone, but only to one pin of the jack itself.

    Any ideas?
     
    Last edited: Dec 21, 2009
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I don't know what is a Cmos speaker.
    The 10uF output capacitor has a value so low that it will feed only high frequency squeaking sounds to a real speaker. Use 470uF and use a good 8 ohm speaker.
    The max output of the LM386 with a 9V supply is only 0.45W which is about as much as a cheap clock radio.

    EDIT:
    I saw the video. It had sound that was very tinny without bass frequencies because the speaker is too small and has no enclosure. The enclosure stops bass from the rear of the speaker from coming around to cancel bass from the front of the speaker. The enclosure must not be too small.
     
    Last edited: Dec 21, 2009
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  4. dave

    Dave New Member

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  5. TheNewGuy

    TheNewGuy Member

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    The 470uF capacitor helped alot. But I think it is the copper wire, because when I touch a 10uF capacitor between pins 1 and 8, even without any imput connected, I hear a lot of static and I can clearly hear a man talking, but can barely make out what he is saying.

    The reason I used this insulated copper wire is because it is easy to solder for my inexperience, but I guess I'm going to have to find some real wire.

    EDIT: But some people are saying it isn't the copper wire...???
     
    Last edited: Dec 22, 2009
  6. TheNewGuy

    TheNewGuy Member

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    Here is a picture of it...
     

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  7. caster.cp

    caster.cp New Member

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    As far as I could tell from your previous post, TheNewGuy, you haven't conected the ground of your input to the ground of your amplifier, right?
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Your speaker is small and does not have an enclosure so it will produce no bass frequencies.
     
  9. mneary

    mneary New Member

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    The coating on your wire isn't causing the problems.
     
  10. TheNewGuy

    TheNewGuy Member

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    The thing is though I am picking up radio!
     
  11. caster.cp

    caster.cp New Member

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    You act both as an antenna and as a capacitor to ground when you touch the circuit. We, humans, contrary to popular belief, are great conductors. Strange things happen when you touch a circuit that's not properly grounded.

    Still, you said that you were only conecting one pin from your audio source. That's ok, you want a mono output. But are you connecting the ground of the audio jack to the minus pin of the battery??
     
  12. TheNewGuy

    TheNewGuy Member

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    Bingo! It worked! No more radio!

    But still no bass, I think it is the enclosure also. I have a 1,000uF 35v Capacitor (same voltage as the 470uF Capacitor hooked up), will I get less distortion and better bass (compared to the youtube video posted above?) with it? The audio comming out of it is still distorted.

    I can take a video of it if you guys want...
     
    Last edited: Dec 23, 2009
  13. gary350

    gary350 Well-Known Member

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    The LM386 IC makes a nice audio amp. Easy circuit to build too. I connected 2 of these in series it has a gain of about 40,000. as I recall. I had to put a volume control on each IC. Volume up 95% on the first IC and volume up about 50 to 60% on the 2nd IC I can hear people talking 1/4 mile away. It is pretty amazing. I am using a 10" speaker on the input as the mic and ear phones on the output. The volume control on stage 2 is very necessary to set the sensitivity.
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The LM386 will have a distorted output if its volume control is turned up too high so that the output is clipped. Clipping is when the output power is only about 0.45W like a cheap clock radio.

    Bass from a speaker depends on whether the speaker has enough quality, enough size and an enclosure that is designed for it.
     
  15. transistor495

    transistor495 Member Forum Supporter

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    Harman/Cardon sounds excellent. Their enclosures/drivers/power supplies are well designed and the output is truly unbelievable.
     
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Harmon/Kardon has always been a pretty good American Hi-Fi equipment manufacturer. Now they own many excellent quality American brands.
    Look in Google for Harmon International.
     
  17. TheNewGuy

    TheNewGuy Member

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    Oh, I forgot to even put a volume control. That could be why.
     
  18. gary350

    gary350 Well-Known Member

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    That is exactly right. That is why it needs a volume control on each stage. First stage has to be adjusted just below the level where clipping starts. The second stage has to be adjust too.
     
  19. TheNewGuy

    TheNewGuy Member

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    Hey Everyone,
    Sorry for all the questions.... :(

    How would I go about adding a couple of LED's to this schematic to make them a VU Meter (like this one) on a breadboard? (I'm going to radioshack today to get a breadboard).

    EDIT: Almost forgot to attach the schematic :p
     

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  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Use an LM3915 or LM3916 IC to drive 10 LEDs in a VU meter.
    adding another LM386 IC or two to your amplifier can drive a couple of LEDs and make them blink to the beat of the music.
     
  21. TheNewGuy

    TheNewGuy Member

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    That chip is so cool! The possibilities are endless! I'm watching videos on YouTube about people who used the chip, dang! I love it!
     

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