Need Help With Small Stereo 4W 9V amp

Discussion in 'The Projects Forum' started by bubbagump0, Jul 10, 2007.

  1. bubbagump0

    Thread Starter Member

    Jul 10, 2007
    26
    0
    I am building some small, portable speakers. I have found some great speakers (8 ohm, 2-4W), but am having a lot of trouble finding a good amp for these speakers. I am planning on powering it with a 9V battery. I am going to be putting the amp and spaekers in a compact space, so I need a very small stereo ampl. I wish I could just design my own amp just for this purpose, but because I am very new with audio, that is not possible. If anyone knows of any amps, kits, schematics, or sites where I could learn to build my own amp, PLEASE inform me.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Here is a 4W audio amplifier from www.discovercircuits.com that is powered by 8 to 12 volts. If you intend to handle stereo you will need to consider building two such amplifiers.

    If you are thinking of using a standard 9V transistor battery, you are going to have difficulty getting any useful life from the batteries.

    hgmjr
     
  3. Gadget

    Distinguished Member

    Jan 10, 2006
    613
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    Well, using the formula "Vpp squared, over 8R" we can see that the maximum RMS power you can get using 9 volts into 8 ohms using a single ended amp (not taking loss's and VD across semis into account) is a little over 1 watt.
    Using a Bridge configuration (2 amplifiers working in opposition across the speaker) 4 x that power ( or 5 watts RMS) would be the max (assuming no loss's) power.

    As hgmjr has suggested, a 9v (PP9 style) battery would not hack the pace, and a pack made from AA's or larger would be the bare minimum required to get any usefull life and current delivering ability.
     
  4. John Luciani

    Active Member

    Apr 3, 2007
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  5. bubbagump0

    Thread Starter Member

    Jul 10, 2007
    26
    0
    Well here's the deal. I have a very small space to put these speakers in. Now I can figure out the power source, but the amp is the tough part. I have already looked at ICs, but I cant build my own circuit, so I need a full kit. Also, if I got an amp for say, 8W stereo, then with 9V (forget about battery life problem for now), could it end supplying about 4W to each channel? Can someone please help me find a kit or something? Thanks
     
  6. John Luciani

    Active Member

    Apr 3, 2007
    477
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    Sometimes the IC manufacturers sell evaluation kits.

    (* jcl *)
     
  7. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    I think if you want to take maximum power from a small voltage, you should consider using 4 Ohm speakers instead.
     
  8. bubbagump0

    Thread Starter Member

    Jul 10, 2007
    26
    0
    Well, I guess I need an amp with about 2-4W of power, and I can adjust my power supply to fit it. I still need help finding a stereo amplifier kit. Thanks.
     
  9. mhtplsh

    Member

    Jul 29, 2007
    27
    0
    Use TDA 2005. It is very well made for 12V supply. Can also be bridged to get more power.
    U will find many projects on web of this IC. .
     
  10. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    The only way to do this efficiently is to use a class-D amp, a switching amp. Check the websites of Maxim, National Semi, and Texas Inst (T.I.) to mention a few.
     
  11. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    An LM386 amplifier IC gives a max output of 450mW at clipping into an 8 ohm speaker with a 9V supply. A little 9V battery will last for a while. When the battery voltage drops to 6V then the max output at clipping is only 200mW.

    When a speaker is in a small space then it won't produce any bass frequencies.
     
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