I want to use the output from an MP3 player to go to a loudspeaker, to broadcast bird song in the field - photography is the name of the game. I am told that the output from the MP3 is too weak to go direct to a loudspeaker, so needs boosting. Lokking at the Maplin (UK) site they list a universal pre-amp (N69AW) which seems to have four wires, and a number of amplifiers again each with four wires. Is this a simple matter of connecting the output from the MP3 to the input of the preamp; output from the preamp to the input of the amp, and the output from the amp to the loudspeaker.
As I say, the unit is to be used in the field, so will be battery powered and I would like to have a reasonable range of volume. One unit that is listed runs on 6v- 16v, will the voltage influence volume! It also suggests a 10k log pot for volume control - placed between the signal source and amp, would this be between the pre-amp and amp?

 

You probably don't need a preamp. The MP3 player will have a high enough signal to feed a volume control connected to the input of the power amplifier.

The supply voltage determines the highest sound level before clipping distortion is produced. I don't know if you an hear the harmonics produced when high frequencies are distorted, and I don't know if birds care about distortion. It might scare them away.

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Uncle $crooge

 

If you don't want to build anything, then just buy a pair of battery operated amplified speakers. You know the sort designed to be used with laptops and small mp3 players?

Like these:
http://www.maplin.co.uk/Module.aspx?...kers&doy=17m10

But I wouldn't recommend Craplin, shop around you can buy louder better quality speakers for this price of even cheaper.

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I don't think the photographer wants to wear those cheap and crappy tiny speakers for him to hear recordings of birds. I think he wants the sound to be loud and clear enough to attract birds.

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Uncle $crooge

 

You may well want a "bridge amplifier". A single-ended amplifier (which is very common) working off a 6v supply would be configured so that one terminal is 3v while the other swings from 6v to 0v. So the speaker sees +/-3V.

In a bridge configuration off of 6v, when there's no signal both speaker wires are at 3v. But with a signal, one wire will go to a higher voltage and one wire goes lower. So the peak signal is +6v on one wire and 0v on the other, and the speaker sees +/- 6v.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

Yes, you will need it to be clear and natural sounding to attract the birds. A portable stereo CD player might be ok if you can find one with a line in/aux in. Or of course put the bird mp3s onto CD.

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Angry!? I'm absolutely electrolytic!

Will have to make do with myspace now I guess...

 

A cheap car stereo system, providing it has a aux in of course.

I wouldn't worry about quality too much as most birds can't hear past 5kHz, just record it onto tap and use a cheap portable cassette player.

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tony-ellis: I'd second Hero999. My son left behind a pair of amplified speakers, battery powered, that were made for a portable radio or CD player. The sound is excellent, all things considered. Someone must still make those. Almost made to order for your application.

FYI - the batteries were installed internally but AC adapters could be attached.

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stevez