audio amp

Discussion in 'General Electronics Chat' started by ees1, Jan 7, 2008.

  1. ees1

    Thread Starter Active Member

    Jan 7, 2008
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    I would like to DIY an audio amp for mp3 players. Now I have mp3 player and two 8 ohm speakers(left and right, 2x1W) for desktop.

    Does anyone have circuit diagram for 2 channel (right and left) audio amp?

    Thanks
     
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Google minty amp

    Fresh breath and deafness are a unique combination.
     
  3. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    www.diyaudio.com is the best place to go for audio stuff, my friend is a total audio-nutcase and that's where he lives :)

    Steve
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    You can base your amp on two LM386 amplifier chips (one for each channel). They can supply 1W to a speaker when fed with 12V.

    You should check the "Projects Collection" section for some help and guidance.
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    A "speaker" that is rated with a max power of only 1W is pretty small. From headphones?
     
  6. ees1

    Thread Starter Active Member

    Jan 7, 2008
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    speakers do have 1W type.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    A 1W little speaker is only good for playing the sound from a rooster, certainly not for music.
     
  8. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
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    The important thing is the diameter of the speaker. A 4" speaker with a wheezer cone can give a good sound. Check the Visaton model FR10. I bought a FR10 speaker from them (the 4Ohm model) and I was admired with the sound quality. And I only used a open baffle made of expanded polystyrene to test it (a plate with a 4" hole, to be more precise).

    Here it is:
    http://www.visaton.de/en/chassis_zubehoer/breitband/fr10_4.html
    And the 8Ohm version:
    http://www.visaton.de/en/chassis_zubehoer/breitband/fr10_8.html
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    The Visaton 4" speaker has no bass and the level of the highs is all over the place.
    Its sensitivity is very low so 1W won't be much louder than headphones laying on a chair.
     
  10. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    Anyone know a good website on the physics of speakers and their performace (THD+N) with audio amps?
     
  11. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
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    Although it as a sensibility of only 86dB/m (I agree that was low sensibility), believe me that a cheap speaker is far much worse. At 1W it is perfectly audible and gives a good bass (very good for a 4" speaker). I tested only one channel at 4W and was audible outside my house, which walls are not made of wood, I must say. So it was quite loud. The bass was reasonable too (of course it depends if you have an enclosure or not, even a simple baffle works). I often to the tests with classical music, that has a wide range of frequencies (lows and highs).

    A perfect solution would be to use a woofer and a tweeter (if not a sub woofer, a bass, a midrange, and a super tweeter), but that would be overkill for this little amp, wouldn't be? I even admit that the speaker I suggested would be overkill in this situation. So, would you really spend a little fortune on expensive speakers for a LM386 amp project? Because I wouldn't (you can see that I suggested two cheap 2 1/2" speakers for my "Portable speakers" project).
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    I replaced the cheap 3" speaker in my clock radio with a much better 3" one.
    I replaced its cheap amplifier with my own 1W one.
    I added bass boost and linked the volume control to it so at low level the bass boost was max (1W), at half volume the bass boost was less (but still 1W) and at max volume the boost was flat (still at 1W). It sounds fantastic.

    I had RadioShack speakers with a 4" woofer and a pretty good dome tweeter in a sealed cast aluminum enclosure. They had much better bass than the 4" speaker you showed.
    I bought them on sale for a very low price. They were rated for 40W but the woofers were stamped 5W.

    My computer speakers have 3" full range drivers with big magnets. They are driven with a bridged amp IC with 4W each. They sound fine.
     
  13. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    www.diyaudio.com

    If they don't know something dealing with audio, then it doesn't exist yet. These guys are complete fanatics and can be very technical!

    Steve
     
  14. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    The speaker I've mentioned is a full-range. It is designed to have a flat response, and not an improved bass response. I would prefer a speaker with a flat response than one with a great bass response, but that is my personal opinion. Also, I don't hear heavy metal or hip hop, and I believe if I heard classical music using only a woofer it would taste horrible for sure (without the brilliant highs of the violins and the flutes). A far as I'm concerned, 100Hz is sufficiently low for me.

    I admit that it is not a very good speaker, but it is a reasonable one and produces a high quality sound considering that is relatively cheap (11Eur) (and I say that based on my live test, not based on a frequency response graph). What would you expect from a 4" full-range?

    Here is a second opinion:
    http://www.diyaudio.com/forums/showthread.php?threadid=93617&highlight=
    http://www.diyaudio.com/forums/showthread.php?threadid=46240&highlight=

    P.S.: I don't believe that a cheap 3" speaker can produce a good sound. I know because I've got one. And I don't think that a 4" speaker can be considered a woofer. A bass? Maybe. However, I do believe that "RadioWoodenHouse" is quite a crap. :D
     
  15. -Excalibur-

    Member

    Jul 20, 2008
    19
    0
    You could buy a cheap pair of Harman/Kardon 19.5's off e bay, they are 3" speakers that sound excellent for what they are (my opinion) then you can extract the drivers to use with your amp (though there isn't much point unless you aim to make it portable (since there is an amp in them, and quite a good one at that for desktops, but it runs off 15V AC, and has a bass increase that is permanant)
     
  16. Audioguru

    New Member

    Dec 20, 2007
    9,411
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    Speakers don't make noise. Only when they play guitar fuzz and country music.

    DIY Audio.com has a forum where they talk about little full bandwidth speakers in a special enclosure sound good but not very loud.
    Usually a woofer and tweeter are used in an enclosure designed for them. Sometimes a midrange speaker is added.
    Usually an additional sub-woofer is used.

    The physics of speakers is a majic art. It is difficult to predict if a speaker design will have many resonant peaks or no bass and no treble. Good speakers have good bass and treble with a flat frequency response.
    One excellent speaker had its sound changed by the fumes from jet fuel. Other speakers are affected by humidity.
    Most speakers have low distortion unless they are defective or are very cheap.
     
  17. dileepchacko

    Active Member

    May 13, 2008
    102
    1
    Hi

    From your explanations, certain thinks are not clear

    1. Power supply for your audio amplifier
    2. Noise level is not mentioned
    3. Required wattage is not mentioned

    1W speakers will not provide you a good audio system, you need at least 10W speaker system, any way i will suggest you to go for LM1877. It is a stereo amplifier which will provide 2W/channel. Its having Wide range of supply voltages. I have attached the data sheet of LM1877 in this mail.

    nothing is impossible.
     
  18. Audioguru

    New Member

    Dec 20, 2007
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    The LM1877 in the DIP package will be discontinued in a few weeks. National list as a "lifetime buy".
     
  19. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Good time to change over to the SOIC Wide IC.

    Either that, or buy a few of the DIPs for spares. Lousy time to make a new design for an IC with last-time buy in effect.
     
  20. Audioguru

    New Member

    Dec 20, 2007
    9,411
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    Good speakers have fairly low distortion.
    Cheap speakers have high distortion.

    Good speakers have wide flat frequency response.
    Cheap speakers have no bass (or sound boomy) , no high treble (or sound shrieky) and the remaining frequencies are all over the place.

    A woofer must have its enclosure built according to the detailed spec's of the woofer.
     
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