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amplifier

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tdag

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I need to do a school project, can anyone tell me how I can build a hand held amplifier, something that I can point towards and hear a person talking from about 30 feet away. thanks
 
30 feet is such a long distance that an amplifier will need a high gain. With such a high gain, the microphone will be so sensitive that it will probably hear the amplifier's output device (speaker or headphones). The results are guaranteed to produce acoustical feedback howling.
A solution is to record the distant sound with the amplifier's output device turned off, then play it back later with the microphone disconnected.
 
tdag said:
I need to do a school project, can anyone tell me how I can build a hand held amplifier, something that I can point towards and hear a person talking from about 30 feet away. thanks

Try searching for 'parabolic mike' or 'shotgun mike', as Audioguru says feedback will be a problem, so you will need to wear headphones.
 
Nigel Goodwin said:
tdag said:
I need to do a school project, can anyone tell me how I can build a hand held amplifier, something that I can point towards and hear a person talking from about 30 feet away. thanks

Try searching for 'parabolic mike' or 'shotgun mike', as Audioguru says feedback will be a problem, so you will need to wear headphones.

Yeah the "amp" is not the problem. All the amp can do is turn up the volume, any op amp can do this. But you need to be able to focus the listening area or the sound of someone 30 ft away can be overwhelmed by ambient noise- wind, cars driving by on the street in the background, birds, etc. Focusing requires a special mike.
 
I take it then your school project is merely to build the amp itself, not the whole system? As Oznog says, it can be done with an Op-amp very easily. I'd suggest using the largest power supply you can get for it, and make the amp itself a low noise model, as you'll want to support the largest dynamic range you can. I won't post a schematic, though I think I know what you want, just I tend to get things wrong :x
 
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